DBA Notes

DBA NOTES WORKING WITH XMANAGER Xmanager is used to work with with GUI applications of Linux server from client node. Steps to work with Xmanager: 1. In the client, on desktop [or from the menu] we can find Xmanager 2.0  Xmanager Passive. Double click on it. 2. In the Telnet or Putty window login to linux and export or set the DISPLAY variable. Ex: export DISPLAY=192.168.0.11:0.0 [ 192.168.0.11 is IP address of client machine] 3. Test Xwindow is opening or not using ‘xclock’ command in telnet/putty window INSTALLING ORACLE 10G Pre-requstics for installilng oracle • We must have o/s user • O/S user must belong to dba group • We must have staging area [Where Oracle S/W dump exist] • We need adequate free space [ 3 to 4 GB] Steps of install oracle • Start x-manager passive • Login into OS Account • Go to stage area (i.e. open the location of software) • Export or set DISPLAY • To perform installation,we need to invoke OUI by executing setup file[ OUI – Oracle Universal Installer] • Run the executable file ‘./runInstaller’ For installing oracle , we have to specify oracle home dir which can be created using mkdir command. While performing installation we may face same error like (OUI-10094 problem in saving invertory installation ,connot contain /home/oracle/product/10.2.0/dbs/inventory/contents XML/oraclehome/props (perimisson denied)) Because while installing the oracle 10g first time some information will be stored in /etc/orainventory/contents/inventory.xml. In this xml file the link for some files are stored. To access this link files while installing the next time we have to give the perimision for that files by using chmod command. Chmod 777 /etc/orainventory/contents/inventory.xml It is better to give file perimission to mountpoints because these are so many files in the xml file,while installing it succeeds or not the path of oracle home is stored in that file. We need to access these files because while installing it reaches for the file link root.sh in xml file While installing it ask us to execute root.sh this is mandatory because if we execute this file it copies files like oraenv files Page 1 of 102

DBA NOTES

This file (root.sh) must be executed as root user only [root@linux ~] cd /oraDB/kittu/ohome/root.sh Then it asks questions like ( the following env variable are set as ORACLE_HOME=kittu, ORACLE_HOME=/oraDB/kittu/home Enter full path of local bin dir [/user/local/bin] The file “dbname,oraenv,coraenv” already exe in /user/local/bin overwrite it(y/n) All file are extracte from source file called praductions.jar(jarjava archeive) script this command will capture all the acivites that done by terminal or user Syn:- script filename Script abc All the activities done by the user after running script will be copied into file called abc To exit from script ,type exit Or stop capturing To see the activities use more command All these activites are stored in file on server The default name for script file is typescript Specific prerequestic checks Summary oracle db10g 10.2.0.1.0 In real time envi ronment, we need to seen all the activities performed by us to client.what we need to send to client must be given by the client in documentation. This is also called as ticket. These files are called log files The naming conversion for log file is Log_ticket_timestamp.txt For sending this report, we need to make a clear view of activities in a file on local pc Steps to place logfile in local pc • Right click on session and select changesettings • Select session logging and choose log all session output and browse a location to store information and then click apply. From then whatever we fire on that session will be stored into that file including output generated by command .after finishing executing all commands and completion of work follow the next step • Again click on session and select change setting • Select sessionlogging and then choose one and then click apply

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DBA NOTES 2nd Method Of Installation using VNC [Vertual Network Computing] Vnc server is present on server and vnc viwer is present on client We need to start vnc server on server through our session and must open vnc viwer on client To start vnc server Syn:- vncserver Then vnc server is started on server. When we start vnc server it asks for password for frist time. Enter password whatever you like. After entering the password it create hidden directory called .vnc. This file is created under home directory of user. This directory consists of files like password,files,startup files,log and pid(process id) files . They are passwd startup linux6:1.pid linux6:1.log Linux6(hosthome):1(port).pid In server,every vnc connection is created with portnumber its starts from ‘1’ next connection is ‘2’ We identified this port number from a line where vnc is started .this file is new’linux6:1(kittu)’ desktop is linux6:1 To search whether vnc started or not Ps –of |grep vnc To kill process:For this we must have the process id of vnc server. This pid is stored in linux6:1.pid file  more linux6:1.pid ps –ef |grep vnc kill -9 6470 Then vnc process is stopped or killed How to start vnc server from client and how to acces vnc server from client?  open o/s user type vnc server and press enter enter passwd if we open vnc server for first type. identified the portnumber of vnc server Linux6:1 open vnc viewer and type ip address of server along with portnumber 192.168.0.102:1 Enter the passwd and press enter Then we connect to x-server through vnc viwer

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DBA NOTES

What is difference between vnc server and x-manager In x-manager, we have to set display. In this if we close the session in the middle of installation or the system is shut down .then installation stops in middle. But in vnc server the installation is being done on server. So if we close the session in the middle of installation or system (pc) is shut down ,the process of installation does not stop because this is done at server level. we can get back the old session by opening vnc viewer in shared mode by entering ip address with portnumber and passwd .we can open this session on another pc also. Screening: Screening is the concept of maintaining the session ‘s data available when close the session For exemple ,when we are working with file in ‘vi’ editor we modified 100 lines and close the session with out saving the file. Actually the file will not be modified at this situation. In this case ,if we use screening ,we can retrive the modification as usual what we had done. This is possible by following the below steps type screen command do the modification to the file whatever we want close the session its given with name screen 0 each and every screen is identified by socket number we list the screen by using command syn: screen -ls 9501.pts -4 .linux6  socket number => the local screen is attached to the session by using the following command Syn: screen –x socketnumber this screen retains the session and we can do the activites what we want to do in previous session actually vnc is used for gui mode and screen is used for cui mode oracle 9i software occupies 1.6gb oracle 10g software occupies 1.26gb

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DBA NOTES

CREATING ORACLE DATABASE The installation of database is done in 2 ways  Manual process  DBCA (Database Configuration Assistant) The requirements for installing database:  We must have oracle software installed  We must have user account  We must have adequate freespace Installation of database using manual process:1. We must set the environments for database ie., we must set values to environment variables like ORACLE_SID, ORACLE_HOME, PATH . Fallow the below steps to set environment $export ORACLE_SID= dkittu $export ORACLE_HOME=/u001/kitty/mysore (software installed location) $export PATH=$PATH:$ORACLE_HOME/bin

ORALCE_SID will be database name. So SID must be same as of the database name we want to create. 2. create the oracle initialization file init+sid.ora in $ORACLE_HOME/dbs directory. In this file we defined some parameters required to create and manage a database. The file name should be in the format init+$ORACLE_SID.ora . Ex: initdkittu.ora The file should be created with following parameters  db_name = dkittu  db_cache_size=500m or 50000000  shared_pool_size = 50m  log_buffer =10000 Undo_tablespace = undotso1  undo_management = /oraDB/kittu/kittudb/c1.ctl  compatible= 10.2.0.1.0 It is better to save and create database files in some particular location

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DBA NOTES 3. After completion of above process  connect to sqlplus as sysdba and issue command startup nomount. $sqlplus SQL>enter username: sys as sysdba Password: SQL> startup nomount

4. Now create the database using the following command Sql> create database dkittu Datafile '/oraDB/kittu/kittu_db/system01.dbf' size 500m, Logfile group 1 '/oraDB/kittu/kittu_db/redo01.rdo' size 5m, group 2 '/oraDB/kittu/kittu_db/redo02.rdo' size 5m, Undo tablespace undots01 Datafile '/oraDB/kittu/kittu_db/undo01.dbf' size 50m;

After executing above statement, database is created is displayed. Then execute the below post scripts 5. Post steps: (scripts) SQL> @$ORACLE_HOME/rdbms/admin/catalog.sql

Instead of writing $ORACLE_HOME we may use ‘?’ This script creates all the dictionary views After the completion of above script, run below script SQL>

@$ORACLE_HOME/rdbms/admin/catproc.sql

This script creates all scripts for all procedural scripts  now connect to system/manager. Type below one sql>connect system/manager

Connected SQL> @$ORACLE_HOME/sqlplus/admin/pupbld.sql

This script creates security files

 sql> conn sys as sysdba  sql> shut immediate Database closed  sql> exit Now we exited from SQL PLUS ---------------

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DBA NOTES

Same process is required to create log some modifications required in initialization file and create database. 1) $export ORACLE_SID= dbcherry $export ORACLE_HOME=/u001/kitty/myhoome (software installed local) $export PATH=$PATH:$ORACLE_HOME/bin Then create initialization file 2) initdbcherry.ora db_name = dbcherry db_cache_size=500m or 50000000 shared_pool_size = 50m log_buffer =10000 undo_tablespace = undotso1 undo_retention=99 control_files= /oraDB/dittu/database/cs.ctl undo_management = auto compatible= 10.2.0.1.0 Then excute the below statements after executing 3 point above executed create database dbcherry sysaux Datafile ‘/oraDB/kittu/databases/sysaux.dbf’ size 50m, datafile ‘/oraDB/dittu/database/system.dbf’ size 350m, Logfile group 1 ‘/oraDB/kittu/database/redo01.rdo’ size 5m, group2 ‘/oraDB/kittu/database/redo02.rdo’ size 5m, Undo tablespace undots01 Datafile ‘/oraDB/kittu/database/undo01.dbf size 50m; Then execute the post scripts Note: - Database name and Oracle SID must be same

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DBA NOTES Creating Database Using DBCA( Database Configuration Assistant) 1) For this we had to run X-manager passive and export display 2) Set environment variables like ORACLE_HOME, PATH Don’t set ORACLE_SID, because we give this SID in creation itself 3) Don’t create initialisation file. It also created during database creation 4) After exporting ENV variables, type dbca and press enter. Then the below steps takes place Welcome screen 1) Operation Select operation you want to perform Create database Configure database options is database Delete database Manage template 2) Database templates Select template from following list to creater database General purpose Transaction processing New database 3) Global databasename: ramu It is consider as ramu.appworld.com sid: ramu 4) database connection option Select the mode in which you want your database to operate by default dedicated server mode (one user) shared server mode (more user) 5) Initiazation parameters By default it takes some values if not we can modify those values memory o typical o custom shared pool-5000000 buffer cache=3k javapool=25000 large –o pga ---1500000

charactersets o use default dbsize o use unicode sort area size 524288 o choose form list

file locations 1)create serverparameter file Trace file defination Userprocess-adim /udump Background process admin/bdump Core dumps admin/cdump

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DBA NOTES Database storage Logfiles System files Controlfiles 7) create options create database save as templates OK Then tempfile is displayed which displays complete information of database Note: for 10g we have some modifications in creation To indentify whether database is down or up: Connected to idle instance means database is down This envinorments varibles values are only with that session.to make that values permanent,save this value in bash_profile. How to we maintain multiple database in one o/s user in a server This is possible by using fuction in bash_profile each function caontain information envinorment value for one database Syn: function() { Export oracle_sid=dbname Export oracle_home=myhome Export PATH=$ORACLE_HOME=/bin } Define the functions .bash_profile file When the user login into account,this functions are loaded into memory. To execute particular function type below commad in shell prompt Syn: $functionname Ex:- $database Then the envinorment variables defined in database are set To switch into another function ,just type that name and press  To check whether database process is started or not use below command. $ps –ef | grep smon When the database is started the process smon is started. Homedirectory: - is the location where the files related to that particular user were navigated. Database: - is the location where the database files are navigated.

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DBA NOTES

Generally in oracle there are 2 main users 1) sys as sysdba 2) system. Sys as sysdba:- This is root login account through this user we perform najor activites like.     

Starting a database Shutdown the database Removal of database Monitoring the database Taking backups

This is recommended to do minor activites like creating tables  Creating users  Altering tables,data There is no password for sys as sysdba. It has the highest privileges of any database. System :- Through this user we perform the low level activities as we mentioned above. The password file system is manager. To connect to system: Sql> connect system or sql>conn system

To run the script in sql use the below command :Sql>@scriptname

Generally when we are creating a database we have to perform 2 phases ;1) Configuring Instance 2) Configuring Database 1) Configuring Instance : - instance is nothing but memory this activity is done creating Init + oracle_sid.ora When instance is started in background two things are started a) SGA b) BACKGROUND PROCESS

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DBA NOTES When we issue startup nomount,it reads initdb.ora and allocates memory to sga and instance is started Sga is space reserved for memory(ram) to database 2)configuring database When we write(create database statements) Database is created After this 3 files are created.they are Datafiles(dbf0 Controlfiles(ctl) Redolog files(redo) After this we have to perform post steps Sizes for software Oracle 9i-----1.6gb Oracle 10-----1.26gb Q) how to change the accounts of bash shell from k-shell This can be done in /etc/password file Change bash from ksh fro the uer which we want to change save the file and exit before doing any modification in passwd file it is better to maintance a copy of that file  in bash the autoexe file is bash_profile in ksh the autoexe.file is .profile When we are changing the shell the data and files in the former shell is available to later shell

Oracle memory Oraccle memory is of 2types .sga (system global area) or (share global area) .pga (process global area) Sga is space reserver for oracle database It is shared memory where the user can share the resource of sga sga basically contains three parts in fundamental method Db_buffer_cache sharepool later one db_buffer_cache shared pool javapool and large pool sga contain five components like db_buffer_cache sharepool logbuffer largepool javapool

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DBA NOTES

db buffer cache we will stored recently used data in buffer cache.if the user request is present in in buffer cache it sends it to ueser . sharepool it contain parssed sql information it translates the sql statement to sql understandable language logbuffer it contains trasactional data javapool it is used for jvm operations sga should be more than 100mb sga should be minimum 100-200m the size of sga con’t be more than the 1/3rd size of ram how to change sga size sga size can be changed by chaging the parameter values in init.ora the total size of sga is determined by a parameter sga_max_size show parameter sga_max_size we can also know sga size when we startup some data is displayed showing some sizes total shared global area 165007897 fixed size ---------------------variable size ----------------------database buffer ----------------------redo buffer -----------------------bouncing the database shut down the database and again start the database is said to be bouncing the database

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DBA NOTES

INSTANCE:

Instance is combination of SGA and Oracle Background process. • • • • • • • • • •

when we do startup oracle will allocate SGA and background process are started which are mandatory to run oracle. This is called Instance. Instance opens database files. Each and every thing is performed by Instance. All the logical manips like creating, reading, writing, etc., are done by instance. All the files are managed by instance. User cannot have access to files without instance User just cannot to instance not to files. User is able to view and perform data(manips) through instance only. Making things available to user is done by instance. Instance is nothing but ORACLE_SID. We can create database with unique.

Three Phases When We Are Starting Databases:1. Instance : At this phase Instance will allocate SGA 2. Mount: At this phase Instance opens way to database files 3. Open: Finally database is opened  When we shutdown the databse, Instance is closed and all the memory (SGA) is deallocated, now we can open the database files (datafiles,logfiles,control files). There are many ways to start the database: 1. We use this when we are creating or altering databse. This stage is used for maintainance of database ie., If we want to increase the size of datafiles, locations of files and if any issues occurred in database. Sys: startup nomount; Alter database mount; Alter database open

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DBA NOTES

2. Startup Open; Alter databse open; 3. Startup: It is used to open a database PGA(Process Global Area) It is memory reserved for each user process connecting to oracle db. PGA is sessions private information. It is external to PGA. Every connection has one PGA. This is private to that connections. Memory is allocated when process is created and deallocated when process is terminated. ORACLE PROCESSES There are 3 types of processes. They are  Server Processes  Client Processes  Background Processes Server Process : When this session is established, server process is created. Connects to oracle instance and is started when user establishes a session. To handle the requests of client process, user process, connected to instance server process is created of behalf of each users app can perform the one or more of following: • •

Parse and execute the sql statements issued through the application (client process) Returns result is such a way that the application can process the information

Client Process: started at a time a databse user requests connection to oracle server. • Client process is a process which is created when client software is started. • When we execute sql plus from $ prompt ,sqlplus becomes client process. • The client proces is a process that sends message to a server, requesting the server to perform a task (service). Client program usually manage the user-interface portion of the application, validate the data entered by the user, dispatch requests to server programs and sometimes executes business logic, the client bases process is front end app that the user sees and interact with Hand shake: When we start client process (ie., when we five sqlplus on shell prompt) before this process interact with instance, the server process interact with client process. This is called handshake. Parent process: For every process there is a parent process. When we execute sqlplus, from shell then $prompt ID becomes parent process ID to sqlplus. ie., shell spanned a process……. Lsnrctl is a software which is executable in ORACLE_HOME/bin Page 14 of 102

DBA NOTES

LOCAL CLIENT PROCESS AND NON LOCAL CLIENT PROCESS Local Process: When the connection established in server through shell prompt, Then it is said to be local process. Non-Local Process: If the connection established out of the server, then it said to be NonLocal process DBA provide user/passwd to APP developer to connect to database we have configure the database which we wish to connect in local pc. In this case client process is running on pc. For each client process there is a server process we identify client process on server, when we start sqlplus as a local client, it is not identified when we start as a nonlocal client. We indentify server process by oracle(It is a Key word)+{ORACLE_SID} Ex: ps –ef | grep oracledbsidnu Output will be Kittu 17148 17147 0 15:20 ? 00:00:00 oracledbsidnu(DESCRIPTION= (LOCAL=YES) (ADDRESS= (PROTOCOL=beq))) Here 17148 is Process ID (PID) And 17147 is Parent process ID (PPID) Parent process ID: for non- local client process is 1 init. Init is helpful to establish a connection. These are client session (or) remote sessions. Oracle is a keyword. It is established in bin. It is in oracle engine. * we run exe files in .profile by setting path in profile as PATH=$PATH:. ORACLE BACKGROUND PROCESS Starts when oracle instance is started, these are used to run oracle database There are 2 tyes: Mandatory  SMON , PMON , CKPT , LGWR , DBWR Optional  ARCH , Pnnn , Jnnn , LCK The mandatory process are mandatory to run oracle. These are started automatically under SGA when we start oracle databse. These must be running in background as long as database is up Naming convention for these process:- ora_process_ORACLE_SID EX: ora_smon_dbsidnu ora_pmon_dbsidnu ora_ckpt_dbsidnu ora_dbwr_dbsidnu ora_lgwr_dbsidnu

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DBA NOTES

RESPONSIBILITIES OF MANDATORY BACKGROUND PROCESS These process started automatically when oracle Instance is started. Its life time is till the instance is opened. ORACLESID is the instance name. *** There is a way to configure database name and Instance name differently SMON [ System Monitor]

It will be used in crash recovery and temp segment cleaning. It recovers after instance failure and monitors temporary segments and extensions. It wakes about every 5 min to perform house keeping activities smon must be always running for an instance. PMON [Process Monitor]

PMON recovers the resources of a failed process. If, MTS(shared server architecture) is being utilised, PMON monitors and restarts any failed dispaches or server process. CKPT [Check Point]

It updates the headers of datafiles, control files with latest SCN(system change number) number.writes the checkpoint informantion to control files and datafiles headers. LGWR: [Log Writer]

Flushes the data from log buffer to redolog files, It writes logbuffer out to redolog files. DBWR [DB Writer]

Flushes the dba from db buffer cache to data files, we can make multiple databuffer. It is for writing dirty buffers form the databse block cache to the databse data files. It only writes blocks back to datafiles on commit or when cache is full add space has to made for more blockes. We can create multiple dbwiters by defining a parameter in init.ora. Parameter: db_writer_processes=2 Data reading from datafiles will be done by server process. Datawriting will be done by background process. ARCHITECTURE OF BACKGROUND PROCESSES When we issue a select statements, shared pool Converts the statements to sql understandable language, Then, it sends it ot db_cache. Then sp server process work is stopped. Now background processes starts working. If the sql statement related information is available in db_cache, it sends it to user. If not, it searches for the info in datafiles and then sends to user. when we issue a transactional statements like inserting,deletion,updation etc., then the copy of the data is maintained in 2 locations: 1. DB WRITER 2. LGWR

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DBA NOTES

It stores in these 2 locations for 2 reasons  dbbuffer : for feature maintanence(faster access)  logbuffer: It is for safety (recovery) When we say commit then data will be sent to redolog files from log buffer by lgwr. The data in db_cache also sent to datafiles by dbwr but copy will be maintained in db_cache for feature maintainence OPTIONAL PROCESS Arch: For Archeiving Archeive process writes filled redo logs to the archive log locations. In RAC, the various arch processes can be utilised to ensure that copies of archieved redologs for each Instance are available to tha other instance in the RAC setup. They need for recovery We start optional process by defining the parameters in init.ora. Log_archive_start=true - it start process Log_archive_max_process=1 [Now it takes only one process. By default it takes 2 processes] Pnnn: These are parallel store process to perform parallel DML activities. It can be used for parallel exe of sql statements or recovery. The maximum number of parallel processes that can be invoked is specified by initialising parameter Parallel_min_servers=1 Parallel_max_servers=10 To stop these slaves: Parallel_min_servers=0 Parallel_max_servers=0 We provide some hints to oracle to use parallel mechanism. Jnnn: Job queue processes To run scheduled jobs in the database Job_queue_process=1 Maximum processes=100 Lck: lock This is available only in RAC instances. Meant for parallel server setups the instance lock that are used to shared resources between instances are hold by lock process.

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DBA NOTES

SERVER PROCESS In Oracle there are 2 technologies  shared server process or MTA(multi threaded architecture)  dedicated server process Dedicated server process: One client process connected to one unique server process is said to be dedicated server process. Server process is complicated to One client. The server process is there, till there is client process. It may be idle(or) working. If 100 members are connected to database 3mb memory is needed. The Architecture we are using is dedicated server Process. Shared server process: Multiple clients connected to unique shared servers is said to be shared server process. It is olderone. The client process will connect to server process through bridge process called Dispatcher process. Dispatcher is mediator between client process and shared server process. We can Reduce the burden and saving some resources on the server. This process is defined in init.ora The advantage of shared server process is saving the resources of the system. RAC: (REAL APPLICATION CLUSTERS) A single database can be access to multiple instances. We have multiple servers for instances, but only one database to all instances. This is called RAC. STANDBY DATABASE Maintianing a copy of instance and database is standby database. The difference is in time log only. DATABASE ARCHITECTURE There are 2 types of databases Architectures.  Physical Logical Physical Architecture is nothing but O/S level architecture. Files that are at o/s level are said to by physical architecture. Physical: 1. datafiles,min(1) 2. redofiles, min(2) 3. controlfiles, min(1) To view the set of datafiles, logfiles,controlfiles.

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DBA NOTES Select name from v$datafiles Select member from v$logfile Select name from v$controlfile Datafile: It stores actual data Logfile: It stores transactions. The purpose of redolog files is recovery in case of failure. Controlfile: stores information and status of datafiles and redolog files, the size of control file is automatically take by system.  When we inserting data, if redo is filled then oracle starts reading to redo, after fitting this is again goes back to redo. This cycle goes on repeatedly. If we enable arching log mode then before over writing the data to previous redlog files, it takes backup to different location. How to identify whether a database is available or not? This is through oratab file in /etc folder. Ex: vi /etc/oratab It stores database names and oracle homes only databases created through dbca are loaded manual creation of databases are to be updated manually to /oratab. It location is changed from one location to another in different O/S. In solaris: /var/opt/oracle LOGICAL ARCHITECTURE:  Schema Object  Non – Schema Object Schema is nothing but a user Seeded Databases:- Default databases Ex: sys, system The objects which reside in the schema are said to be schema objects. Ex: Table, view, index, synonym, procedure, package, function, database name, sequence, etc., The objects which are not associated with schema are said to be nonschema objects. Ex: Tablespace, Roles How to refer an object of schema? 1. Either we login to schema and access the object 2. From different login user. First the user has the permission to access that object, fallow the below syntax Syn: schema object Ex: scott To start database: Sqlplus “ / as sysdba”

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DBA NOTES

DATA DICTIONARY 1. Oracle will maintain entire system data into data dictionary of catalog.sql 2. System data is data which is required for functionality of database. 3. Data dictionary or catalog is set of tables, views and synonyms. 4. When we create database, some files and objects are created both physically & logically. Physically: control files, redolog files, data files. Logically: Basetables tab$ Vet$ File$

fet$ obj$ ts$ luster$ idx$ v$

There tables are extracted when we run created data. we connot access these tables directly. It is very difficult to understand the data in these tables. There are some views to access these tables. These are created when we run catalog.sql VIEWS Tables Idx Synonyms Views Sequences Clusters Database rows Datafiles

dba_tables dba_indexes dba_synonym dba_views dba_sequences dba_clusters dba_db_links dba_datafiles

all_tables all_indexes -------

user_tables user_indexes -------

 Oracle will update the activities in to base tables whatever the ddl activities done by us. Database engine will take this responsibility. Whole oracle is working based on there base tables.  we should use only select statement  only system and sys has dba privileges dba_ :- It will display everything in the database (all users info)  every thing user_ :- It will display only logged in users information  only own all_ :- It will display logged in users info and the objects which have access to that user  own+access Oracle engine will gives access to 9 tables to users by default. All these base tables are objects to know about the objects and the dba objects.

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DBA NOTES

DICTIONARY VIEWS: dba_objects dba_tables dba_indexes dba_ind_columns dba_synonym dba_ views dba_sequences dba_clusters dba_constraints dba_cons_column dba_tab_column session_privs

To know the objects in a database T know about tables info To know about index info To know about the info of index applied in column To know about synonym info To know about views info To know about sequences info To know about source code fro function procedure,packages etc., To know info about constraints To know about constraint columns info To know about table column info. To see session privileges

desc session_privs  only one column when we give grant rde only one privilege is accessed  create session Resource: create table, unlimited table space , cluster,sequence, procedure, trigger, types, operator, index type. user_tab_privs user_sys_privs Dba_free_space Dba_tablespace Dba_data_files

To see user tables privileges To see users privileges To see tablespace size and freespace To see tablespace info To see datafile info

V$TABLES: The views started with v$ are said to be dynamic performers V$database V$datafile V$controlfile V$logfile V$version V$session

Database info Datafile info Controlfile info Log file info Version Session info

SQL: Structured Query Language SQL*PLUS: This will work only in oracle.They are used to format output i :- To insert a statement in buffer ie., adds new line to the sql statement a :- Appends new words to sql statement c :- Change the string and replace it with the required string

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DBA NOTES syn:- c// cl buff: It will clear sql buffer (Clear Buffer) save: by using this, we can save sql statement. We refer these statements as sql statements. To run the sql scripts from any location, we had to mention the location of sql scripts ie., ORACLE_PATH in bash_profile Export ORACLE_PATH = /tmp:/oraAPP:/oraAPP/kittu Usuallly these sql scripts are saved in the location from where we fire sqlplus. How can we capture some output in sql? In unix, it is possible by script command In sql, it is achived by using spool command Syn:sql> spool sql> statements - - sql> spool off Ex:sql> spool a.out sql> select * fromtab;  o/p along with statements are stored in a.out. sql> desc abc sql> spool off How to format column data in sql To know line size :show linesize; To set line size: set linesize 200 To set column size in numeric format :column empno format 9999 ie., it displays column empno with 4 digits To set column size in alphabet format:column ename format a15 Development :- Designing side is said to be development. When we work on new project we are said to be working on development side Production :- After everything is designed and tested then it is deployed into production Query to create user:Syn:- create user identified by Ex:- create user xyz identified by xyz; Granting privilages to user:Syn:- grant connect, resource to xyz; Droping user:Syn:- drop user xyz;

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DBA NOTES To view the source code if views:Syn:- select text from dba_views where view_name=’xyz’; Granting dba to user:Syn:- grant dba to ; Revoke privilage from user:Syn:- revoke from ; QUERIES Views:To see view information Select view_name,owner,text from dba_views; Sequences:- To see sequence number Select sequence_number,sequence_name from dba_sequences; Synonym:- To see synonym information Select owner,synonym_name,table_owner,table_name from dba_synonyms; Indexes:To see index information Select owner,index_name,table_name from dba_indexes To see index column info:Select index_name,table_name,column_name from dba_ind_column; To see row id:Select rowid from ; Constraints:Select owner,constraint_name,constraint_type,table_name from dba_constraints; To see constraint column:Select owner,constraint_name,table_name,column_name from dba_cons_column; Tables:Select owner,table_name,tablespace_name,status from dba_tables; Users:Select username,default_tablespace from dba_users; Tablespaces:Select tablespace_name,status from dba_tablespaces; Database:Select name,dbid,created,open_mode from v$database; Version:V$version has only one column  banner Select * from v$version

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DBA NOTES

Datafiles:Select file_name,tablespace_name,bytes/1024/1024,online_status,autoextensible from dba_data_files; To see datafile in mount stage based on ts index :Select name,ts#,status,bytes/1024/1024 from v$datafile where ts# = 0; Procedures:Select owner,procedure_name from dba_procedures; To see source code:Select text from dba_source where name=’name’; Objects:Select owner,object_name,object_type from dba_objects; Functions:Select owner,object_name,object_type from dba_objects where object_type = ’FUNCTION’; Source code:Select text from dba_source where name = ‘FUNCTIONS‘; Packages:Select owner,object_name,object_type from dba_objects where object_type = ’PACKAGE’; Source code:Select text from dba_source where name = ‘---‘; Triggers:Select owner,trigger_name,trigger_type,table_name,column_name from dba_triggers; Source code Select text from dba_source where name= ‘---‘; Control file:Select name,status from v$controlfile; Log file:Select member,group#,status from v$logfile; Privilages:To seee table privilages:Select grantee,owner,table_name,grantor,privilage from user_tab_privs; To see user privilages:Select username,privilage,admin_option from user_sys_privs;

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DBA NOTES

TABLESPACE MANAGEMENT Tablespace is a logical structure which binds the objects. Tablespace is a container for data files i.e., tablespace is a collection of one or more data files. One database has minimum one tablespace. Tablespace always associated with one or more data files. Database is a collection of tablespaces. It is one to many relationships. - Size of database is size of tablespace. - Size of tablespace is size of data files. - As we increase tablespaces, database size increases. - We can’t create tablespace without data file. - Each tablespace has its own data file. - Redo logs and control files will never grow in size. So we never consider these files in the size of tablespaces. These are key structures. - A data file cannot be shared across tablespace Syntax to create tablespace:Create tablespace data file size ; Ex:- create tablespace ts01 data file ‘/oraAPP/kittu/ts01.dbf’ size 10m;

How do we make tablespace offline? Syn: - alter tablespace ts01 offline;

This means we can’t access the data in the tablespace even we can’t perform select statement. How do we make tablespace online?

Syn: - alter tablespace ts01 online;

To see tablespace name, filename, size of data file: Select tablespace_name, file_name, bytes/1024/1024 from dba_data_files.

To see size of database: Select sum (bytes/1024/1024) from dba_data_files;

Dropping a tablespace: Before dropping tablespace, it is better to make tablespace offline. Syn:- drop tablespace ts01;

In this case only tablespace is deleted but the data files are maintained in o/s level. To delete the files in o/s level i.e. contents and data files (contents means objects i.e. tables, views, etc) in TS. Syn:- drop tablespace ts01 including contents and data files;

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DBA NOTES Increasing the size of tablespace:We can increase the size of tablespace in two ways. 1) we can increase the size of data file Syn:- alter database datafile ‘/oraAPP/kittu/ts01.dbf’ resize 50m;

2) we can add a datafile Syn:- alter tablespace ts01 add datafile ‘----‘ size 10m;

How can we assign tablespace to new user?

Syn:- create user identified by default tablespace Ex:- create user msb identified by msb default tablespace ts01;

How can we assign tablespace to existing user? Syn:- alter user default tablespace Ex:- alter user msb default tablespace chinni;

Not important points:- If datafile is very big, oracle encounters some issues. So we use datafiles max. of 5GB size. - If we doesn’t mention datafile location, it saves that file in ORACLE_HOME/DBS directory - When we enter data to a datafile more than its size, it shows below error. Error:- unable to extend table msb.emp by 128 in tablespace chinni; To see free space of tablespace:Syn:- Select sum(bytes/1024/1024) from dba_free_space where tablespace_name=’CHINNI’;

Nfs mount point:- ( Network file system) All the mount points that are available to us are said to be local mount points. Ex:- /oraDB , /oraAPP , /stage , /u001 etc. A mount point which is placed in another server is said to be NFS mount point. Syn:- mount –t nfs 192.168.0.16:/stage

This nfs creation is done byunix admin. Maintenance of datafiles:- Physical architectureis maintained by and managed by ORACLE ENGINE. There are two ways in work nature: 1) Proactive:- the solution before problem exists. 2) Reactive :- the solution after problem exists. - we can increase the datafile size automatically. - This is possible by making autoextend on. Syn:- alter database datafile ‘----‘ autoextend on;

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DBA NOTES To see datafile and its size dynamically:Syn:- select filename, bytes/1024/1024 from dba_data_files where tablespace_name =’ts’

how can we specify datafile size autoextend upto some size:Syn:- alter database datafile ‘---‘ autoextend on maxsize 200m;

To see maximum size of datafile:- (autoextend) Select file_name,autoextensible,maxbytes/1024/1024 from dba_data_files;

Increase the size of TS by certain size:Alter database datafile ‘---‘ autoextend on next 10m maxsize 100m;

Renaming a tablespace:It is possible only in 10G Syn:- alter tablespace chinni rename to babu;

In 9i, it is not possible to rename a tablespace. To perform this we had to follow the below steps - create new tablespace - move all tables from old TS to new TS Syn:- alter table move tablespace ; Ex:- alter table emp move tablespace venki;

To see table and tablespace name:Select table_name,tablespace_name from dba_tables; To see how many datafiles in tablespace:Select count(*) from dba_tables where tablespace_name = ’;

-- > When we move table from one TS to another TS, the table will be maintained inuser.

BIGFILE TABLESPACE: It is new in 10g. by this we can create very big tablespace of terra bytes size. Maximum size is 4 terrs bytes. Syn:- create bigfile tablespace ts01 datafile ‘---‘ size 10g;

Renaming a datafile:To rename datafile we had to follow the below steps. - make tablespace offline - rename datafile in o/s level syn:- mv

-

< old filename>

rename file in sqllevel syn:- alter tablespace venki rename datafile ‘’ to ‘’;

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DBA NOTES - make tablespace online we rename file in sqllevel to update it in data dictionary. To see user and tablespace:select username,default_tablespace from dba_users;

STARTUP AND SHUTDOWN STARTUP: There are different phases in startup:1) Instance allocation:Memory for SGA is allocated and background process starts.memory is allocated by reading parameters from init.ora. this is instance. Instance started 2) Mount stage:Instance opens control file Database mounted 3) Database openstage:Database is opened. i.e. instance opens datafile and redo logs through control files.because control file contains info of datafiles and redolog files. Three methods to start database:I method:sql> startup

In this method all the three phases are executed at a time. II method:sql> startup nomount

In this stage, only instance is allocated.

Sql> alter database mount;

In this stage the database is mounted. i.e second phase. Sql> alter database open;

In this stage the database is opened. i.e third phase. We issue startup nomount to perform 2 things:1) creation of database 2) creation of control file III method:-

sql> startup mount

In this stage, phase1 and 2 are executed. Sql> alter database open;

Database is opened. Generally we open the database in Mount stage to perform maintenance activities like renaming datafiles, default tablespaces, redologs etc. In this stage we can’t access dba_ views. We access only v$ views.

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DBA NOTES We can’t make system tablespace, undo default tablespace offline. How can we rename datafile of system TS: We can’t make system TS offline in DB open mode, because if we make it offline we can’t access dictionary views i.e. we can’t access users, tables etc. so we rename the datafile of system TS in mount stage only. Steps: open database in mount stage startup mount

 move or rename system TS datafile in o/s level  move or rename system TS datafile in sql level Syn:- alter database rename file ‘’ to ‘’;

 we can also rename undo TS in mount stage only, because we can’t make it offline. To know tablespace datafile names in mount stage: Select ts#,name from v$tablespace where name=’SYSTEM’; Select name fom v$datafile where ts#=0;

We can rename datafile in 2 levels:1) Database level  mount stage 2) Tablespace level  open stage i.e. making it offline and rename it.

Undo tablespace:It is for undo operations. It will maintain old data till we issue commit. SHUT DOWN: There are 4 methods:1) shutdown (or) shutdown normal 2) shutdown immediate 3) shutdown abort 4) shutdown transactional Shutdown Immediate: It is reverse of startup Phase1Database closed All the connections(sessions) connected to instance are killed. All the pending transactions are rolled back. A check point will happen and dirty buffers will be flushed to datafiles. Datafiles and redolog files are closed. Phase2Database dismount stage (Database dismounted) Control file will be closed. Phase3Instance deallocation (Instance closed) Background processes are killed and memory for SGA is deallocated. It does not wait for the users to disconnect from the DB.

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DBA NOTES

Difference B/W Shutdown and Shutdown Immediate:- Shutdown Immediate will kill all the existed users - Shutdown will wait for the users to get disconnected themselves. Alert Log File:All the startup and shutdown activities will be captured into a file called alert log file. The extension is . By default it is stored in /ORACLE_HOME/RDBMS/LOG/.. Use tail –f to display alert file content and update in incremental order.

Shutdown normal:- (Shutdown) When we use this option, all the steps which occurs in Shut Immediate happens, except the first 2 steps.  It waits for the logged in users of database to quit.  It is default option which waits for users to disconnect from the database.  Further connections are prohibited.  The database is closed and dismounted.  The Instance is shutdown and no Instance recovery is needed for the next DB startup.

Shutdown abort:- (Shut abort)  The fastest possible shutdown of the DB without waiting for calls to complete or users to disconnect  Uncommitted transactions are not rolled back  Sql statements currently being processed are terminated  All users currently connected to DB are implicitly disconnected and next DB starting will require Instance recovery.  We use this option if a background process terminates abnormally and when high voltage of power occurs  It just deallocates the Instance

Shutdown transactional  This option is used to allow active transactions to complete first i.e. it will let the current transactions to be finished  It doesn’t allow client to start new transactions  Attempting to start new transaction results in disconnection  After completion of all transactions, any client still connected to Instance is disconnected  Now the Instance shuts down  The next startup of database will not require any Instance recovery.  It will kill users who are idle  In real time, we use S.I and S.A

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DBA NOTES

Startup Restrict:We use this option to allow only oracle users with the Restricted session system privilege to connect to database. i.e. only the DBA can have access to DB. We can use alter command to disable this restrict session feature. Syn:- alter system disable restricted session

Actually we use this when we are in maintenance. So we can’t give access of the database to other users.We can enable restrict session feature after logging to database as sys user. Syn:- alter system enable restricted session

Startup Force:- (Shutdown abort + startup) Shutdown the current oracle Instance with shutdown abort mode before restarting. Force is useful while debugging and under abnormal circumstance. It should not normally be used. Read only tablespace:Read only tablespace allows users to do only reads from the tables with in it. No data manipulation is allowed. This read only option causes the database not to work to these files once their tablespace is altered to read only. This allows users to take advantage of media that allows for readonly operations. The major purpose of making a tablespace read only is to eliminate the need to perform backup and recovery of large, static portion of a database. we can drop items, such as tables, indexes from read only tablespace but we can’t create (or) alter objects in a read only tablespace.

SYSAUX TABLESPACE It is new in Oracle 10g. it is used to store database components that were stored in system tablespace in prior releases of database. It was installed as an auxiliary TS to SYSTEM TS. When we create the database, some database components that formerly created and used separate tablespaces row occupy the SYSAUX TS. If the SYSAUX TS becomed unavailable, core database functionality will remain operational. The database features that use the SYSAUX TS could fail or function with limited capacity.

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DBA NOTES

CONTROL FILE MANAGEMENT  Every oracle database has a control file  A control file is a small binary file that records the physical structure of database. It includes..  Database name  Names and location of associated datafiles and online rdo’s (SCN), tablespace info, archive log info  Timestamp of database creation  Current log sequence number  Check point information  The control file must be available for writing by the oracle database server whenever the database is open  Without control file, the database cannot be mounted and recovery is difficult  It is created at the time of creation of database  We can create maximum of 8 control files  We cannot have any control over control file and its size will be determined at the timeof database creation  It is very small in size and it is static and it can’t be altered  Actually we need more than one control file when the failure of first control file.  If we have ‘n’ number of control files, all the files are same in size and contain same info How can we add one more control file to database? Shut down the database using shut immediate mode Make a copy of existing control file in same location or in another location Syn:- cp c1.ctl c2.ctl Or cp c1.ctl /oraDB/kittu/c2.ctl Add the newly created control file location using control_files parameter in init.ora file. Ex:- Control_files = ‘/oraDB/kittu/c2.ctl’ Start the databse Note:- If we add control file without copying it, it searches for that file when we start the database. So, oracle doesn’t read that file. How can we remove control file? Remove the control file location in init.ora file (parameter file) After that remove the file in o/s level. The dictionary view to get the control file information Select block_size,file_size_blks from v$controlfile Block_size=16384 and file_size_blks=370 Page 32 of 102

DBA NOTES ((blocksize * filesizeblocks)/1024)/1024 -- > we get control file size OR By firing ls –l command in unix , we get the bytes Minimum control files 2 to 4 V$parameter:- Lists status and location of all parameter. V$controlfile_record_section:- Provides information about the control file record status Show parameter control files:- Lists names,status,location of control files

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DBA NOTES

REDO LOG FILE MANAGEMENT Each oracle has redo log files. These redo log files contains all changes made in datafiles The purpose of RDO is if something happens to one of the datafiles, a copy of datafile is maintained in RDO’s which brings the datafile to the state it had before it became unavalible. i.e. it is used for recovery of data. The size of RDO is static. We determine its size in the creation of database. We can’t change its size unless in the maintenance. The idea is first to store the transactional data in log buffer to reduce i/o retention. When a transaction commits (or) check point occurs, the data in log buffer must be flushed into disk for the recovery. It is done by LGWR The redolog of database contains one or more redolog files. The database requires a minimum of two files to guarantee that one is always for writing while the other is being archived ( if the database is in archivelog mode) LGWR writes to redolog files in a circular fashion. When the current redolog file fills, LGWR begins writing to the next available redolog file. When the last available redolog file is filled, LGWR return to the first redolog file and writes to it starting the cycle again. In this case if the first RDO is overwritten the data is lost. This happens when the database is in NOARCHIVELOG mode. This reading of data into another redolog file after filling the former one is said to be log switch process. It is a point at which the database stops writing to one redolog file and begins writing to another file. Oracle DB assigns each redolog file a new log sequence number everytime whenever a logswitch occurs and LGWR begins writing to it. When the database archives redolog files, the archived log retains its LSN. A redolog file that is cycled back for use is given the next available LSN. Archive Log Mode: If the database is in logarchive mode, the database makes sure that online redologs are not overwritten. The filled redologs are archived (or) saved into another location(where we specify the location init.ora file) We set this location in init.ora by using log_archive_dest parameter Noarchive Log Mode: If the database is in noarchivelog mode, online redologs can be overwritten without making sure that taey saved or not. This implies that a database cannot be recovered even if backups were made.

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DBA NOTES How can we know the database is in archive log (or) noarchive log mode: - select log_mode from v$database; (OR) - archive log list Arch background process: Arch is the archiver. Its task is to automatically archive online redologs so as to prevent them from being overwritten. The archiver background process starts if the database is in archivelog mode and automatic archiving is enabled. i.e. taking the data in RDO to some other location is said to be archiving. How can we convert database to archivelog mode: To start the archivelog mode • Shutdown the database • Define the parameters in init.ora parameter initialized file • The parameters are – • log_archive_start=true -- > Necessary in 9i only. Optional in 10g. • log_archive_dest = ‘—‘ -- > locator where we need to archive log files • log_archive_format= %s arc • The files which are archived will be saved in the format as we define in parameter. Syn:- alter system set log_archive_format = ----• Start the database in mount stage • Now fire the command to switch to archivelog mode. • Ex:- alter database archivelog Archived to Noarchivelog mode:• shutdown immediate • startup mount • alter database noarchivelog • alter database open Note:• We can do archivelog and noarchivelog when the database is in mont stage only. Because we must regular the activities to control file and we done this activity in database level • We usually refer redolog file group other than redolog file. Why we need more than one redolog file in a group:This is because to safeguard against damage to any single file. When we create multiple redolog files, LGWR concurrently writes the same redolog information to that files, thereby eliminating a single point of redolog failure. Other files in a group are said to be ___________. All are same in size and contains same data.

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DBA NOTES V$log_history  V$log  V$logfile 

Contains log history It contains group information It contains logfile or members information

Select members ,group# from v$log; It gives groupname and no.of files in a group select member, group# from v$logfile; It returns groupname,logfilenames How can we create a Redo log Groups:-

Alter database add Logfile group ’/oraAPP/redo1.rdo’ size 5m;

(or) Alter database add logfile group 1 ( ‘/oraAPP/redo1.rdo’, ’/oraAPP/redo2.rdo’) size 10m;

How can we drop redo log groups:-

Alter database drop logfile group1;

How can we add a member to existing group:Alter database add Logfile member ‘/oraAPP/redo3.rdo’ to group;

How can we drop a member:Alter database drop Logfile member ‘/oraAPP/redo3.rdo’;

Why we need to drop log groups and members: To reduce the no. of groups in an instance redolog. In the case of disk failures and a file must be located in improper location. Before drop a redolog group (or) member we had to perform the below steps:We can make the status of group as inactive (or) active. Because we can’t drop the current running group. We get the status of group by select group#, archived,status from v$log;

So we forced oracle to switch the curren status to another group . This is possible by using a command like. alter system switch logfile;

Now current status of group changes. *we can do this activity when the database is completely opened. *we can add (or) remove a group and its members is mount stage and open stage also.

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DBA NOTES How can we change binary data to text formate: Strings –a c1.ctl>a

***When we are in mount stage and archive log is enabled. But it shows automatic archival as disabled .when we fire archive log list . Clearing a redo log file:alter database clear logfile group3; It will reinitialized the damaged group Clearing unarchived log file:

Alter database clear unarchived logfile group3;

This can be done without shutting down the database also How can we rename (or)relocates redo log file members:1) shut down the database 2) copy redo log files to new location (or) rename it mv old new 3) startup mount 4) alter database rename file ‘---------‘ to’------------‘; 5) alter database open; Active and inactive redo log files (or) groups: Redo log files that are currently capturing data are current redo logs. Redo log files that is not current redo log group. It is needed for crash recovery . Redo log group that has never been written to is said to be unused rdo. Redo log files after active are said to be inactive rdo’s. Adjusting the no.of archiver process:  alter system set log_archive_max_processes=3;

Q) why we need more than 2 log groups ? Assume that we have 2 log groups. If one log group is in current state and the other group is archiving. After first log group is also filled. But the 2 group is still archiving. Then lgwr doesn’t know to which group it had to write the data generally archiving is slow. So, inorder to prevent this , we need one more group. To stop archive log process:Log_archive_start=false

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DBA NOTES

P FILE AND SP FILE P-File: (parameter file): It is init+oracle_sid.ora file. It is present in ORACLE_HOME/dbs. This file is text file and is editable. From 9i , oracle introduced a new file, it is SPFILE. SP-file(server parameter file): It is binary file and is not editable. If the database contains both pfile and spfile. Oracle starts using spfile only. Because it provides dynamic allocation. What is the solution if init file name is not in proper form ? If the init file is x.ora. then start the database using following command. Syn:-

startup pfile= /ORACLE_HOME/dbs/x.ora

How to create sp file ?

select * from dba_temp_files;

We create spfile from pfile using the below command Syn:- create spfile from pfile;

Parameter to show spfile ?

Show parameter pfile (or) show parameter spfile

If the value column of this parameter shows some value, it indicates that database starts using spfile. How to create pfile from spfile ? Syn:- create pfile

from spfile;

How to edit spfile ? Oracle will not support to edit spfile, to edit it follow the below steps 1) Drop the existing spfile 2) Edit in init.or 3) Create new spfile from pfile 4) Start the database How can we delete a database ? In 9i to drop a database, delete the datafiles, rdo’s controlfiles etc., But in 10g , new feature is introduced to drop a database follow the below steps. 1)open database in restrict mode SQL> startup restrict

2)drop the database SQL> drop database;

Then automatically all the database related files are deleted except init.ora ALTER SYSTEM:-

ALTER SYSTEM set parameter value scope=[spfile/memory/both]

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DBA NOTES Memory the new parameter value will be updated only in database Both the new parameter value will be updated in both spfile and database. Audit files:The files contains information, if we start sqlplus as ‘sys as sysdba’. It also updates when we connected from another user to ‘sys as sysdba’. Who logged in started the database is stored. It contains o/s user name, database name, system name, oracle_home, database user, privilege, time etc., Whenever “we connect to sys user it creates audit files”. Ex:- ora_3702. and

TABLESPACES 1) Permanent tablespaces 2) Undo tablespaces 3) Temporary tablespaces in 10g ,we cannot have more then 65536 tbs. Permanent tablespaces: The tablespaces which are used to store the data permanently are said to be permanent tablespaces. Ex:- system, Sysaux, Etc., Undo tablespaces : Every oracle database must have a method of maintaining information that is used to rollback (or) undo,changes to the database. Such information consists of record of actions of transactions, primarly before they are committed. Such records are collectively referred as undo. Undo tablespace is used to store undo records of database. i.e., uncommitted transactions(pending data). We create undo tablespace at the time of database creation. If there is no undo tablespace available, the instance starts but uses the SYSTEM tablespace as default undo tablespace. It is not recommended option. So create undo tablespace at the time of database creation (or) after that by setting parameter value[undo_tablespace] Creating undo tablespace:  Create undo tablespace undots01 Datafile ‘/oraAPP/kittu/db1/undo1.dbf’ size 50m; We can create multiple undo tablespaces. But there is no use, because we use only on undo tablespace.

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DBA NOTES How the data stored in undo tablespaces? 1000 Old data

UNDO TS

Rollback

1000 updated to 5000 User TS

If the table contains the salary 1000 for some employees. If we update the salary 1000 to 5000. Then the records which contains salary 1000 will be stored into undo tablespace and salary 5000 will be updated into table. If we do commit they remain. Otherwise 1000 will come back to the table We can view the tablespace type from dba_tablespaces Select tablespace_name,contents from dba_tablespaces;

To know which undo tablespace is assigned to database. Show parameter undo

(or) From dictionary view database_properties How to set undo tablespace fro sql prompt? Alter system set undo_tablespace=’UNDOTS01’;

If we set this it is available only for that session. If there is sp file it will be permanent to database because sp file allows dynamic alloction. If there is no spfile we need to specify it in. Dropping undo tablespace:

Drop tablespace undots01;

Resizing undo tablespace: We can resize undo tablespace in 3 ways. adding a new datafile. extend the size of existing datafile Some process as we done for permanent tablespaces. Renaming undotablespaces: Similar to permanent tablespaces. Temporary Tablespaces Temporary tablespaces are used to manage space for database sort operations and for sorting global temporary tables.

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DBA NOTES Ex:If we join 2 large tables, and oracle cannot do the sort in memory(see SORT_AREASIZE) initialization parameters, space will be allocated in a temporary tablespace for doing the sort operation. Other sql operations that might require disk sorting are create index, Analyze, Select distinct, Order by, Group by The DBA should assign a temporary tablespace to each user in the database to prevent them from allocating sort space in the SYSTEM tablespace. TEMP FILES: Unlike normal datafiles,tempfiles are not fully initialized when you create a temp file, oracle only writes to the header and last block of the file. This is why it is much quicker to create a temp file than to create a normal database file. Temp files are not recorded in database’s control files. The implies that are one can just recreate them whenever we restore the database (or) after deleting them by accident. One cannot remove datafiles from a tablespace until we drop entire tablespace. However, one can remove a tempfile View:- dba_temp_files Syn:- alter database tempfile ‘/oraAPP/temp1.dbf’ drop including datafiles;

If we remove all temp files from a temporary tablespace, you may encounter. Error ORA-25153 temporary tablespace is empty  Use the below syntax to added temp file to temporary tablespace Syn:- alter database temp Add tempfile ‘/oraAPP/temp02.dbf’ size100m;

How can we create a temporary tablespace ?

Create temporary tablespace temp Tempfile ‘/oraAPP/t1.dbf’ size 50m;

How can we assigns a temporary tablespace to database ?

Alter database default temporary tablespace temp;

How can we know the temporary tablespace information which is assigned to database? create user x identified by y Temporary tablespace temp;

(or)

alter user x

temporary tablespace temp

How can we know to which user, which tablespace is assigned ?  From dba_users  select username,temporary_tablespace from dba_users; It is better to assign temporary tablespace to avoid everytime assigning it to.

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DBA NOTES USER- MANAGEMENT We connect to database as user only. Creating user: Syn: Create user username identified by password; Ex:-create user kittu identified by kittu;

Changing password: Ex:-alter user kittu identified by ramu;

Lock the user:

Syn:-alter user username account lock;

Unlock the user: Syn:- alter user username account unlock;

Password expire:

Syn:- alter user username

password expire;

Assigning default tablespace to user:Syn:-

alter user kittu Default tablespace chinni;

Assigning temporary tablespace to user:

select * from dba_temp_files; Syn:- alter user kittu Temporary tablespace chinni;

Dropping user:

Syn:- drop user kittu cascade;

PRIVILAGES AND ROLES Privilege: Privilege is a right to execute a particular type of sql statement (or) to access another user’s object. (or) Privilege is right to perform a specific activity. A privilege can be assigned to user (or) a role Privileges are of two types:1)System privileges 2)Object privileges The fundamental privileges:- create session, create table

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DBA NOTES System privilege: A system privilege is right to perform particular action(or) to perform an action on any schema objects of particular type. For example the privileges to create tablespace and to delete the rows of any table in a database are system privileges. To perform DDL activities.  who can grant and revoke system privileges ? • users who have been granted a specific system privilege with the admin option. • Users with the system privilege grant any privilege i.e., DBA can grant system privileges granting and revoking system privileges. Syn:Grant create session to kittu; Grant create table to kittu; Syn: revoke create session from kittu;

Object privilege: Object privilege is the permission to perform a particular action on a specific schema object. To perform DML activities on other user. Some schema objects such a clusters, indexes, triggers, and database links, do not have associated object privileges. Their use is controlled with system privileges. For example, to alter a cluster, a user must own the cluster (or) have the alter any cluster system privilege. Who can grant object privileges Owner of the object A user with grant any object privilege can grant (or) revoke any specified object privilege to another user with (or) without grant option of the grant statement Granting and revoking object privileges Grant:-

Grant select on emp to kittu; (owner) (or) Grant select on scott.emp to kittu ; (dba) Revoke:- revoke select on emp from kitttu; (owner)

how to know the privileges of particular user ? Select * from session_privs; dba_sys_privs view is used to see system privileges all_sys_privs, user_sys_privs dba_tab_privs view is used to see object privileges. Administrative privileges: Administrative privileges that are required for administrator to perform basic database operations are granted through two special system privileges, sysdba and sysoper SYSDBA can perform following operations:  Perform startup and shutdowm operations  After database open,mount ,backup (or) change character set

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DBA NOTES  Create database, spfile  Archive log and recovery  Includes the restricted session privilege Sysoper can perform following operations:  Perform startup, shutdown  Create spfile  Alter database mount/open/backup  Archive log and recovery  Includes the restricted session privilege DBA_COL_PRIVS is used to view on column privileges. Other dictionary views: Column_privileges, table_privileges, all_tab_privs_made, user_tab_privs_made Dba_tab_privs_made doesn’t exists ROLE: Role is a set of privileges Managing and controlling privileges is made easier by roles, which are named groups of related privileges that you grant, as a group , to users (or) other roles, within a database, a role name must be unique, different from usernames and all other role names. Unlike schema objects, roles are not contained in any schema.  who can grant (or) revoke roles? • any user with grant any role system privilege can grant or revoke any role • any user granted a role with admin option can grant (or) revoke that role to (or) from other users (or) roles of database. There are 18 predefined roles. Ex:- connect,resource, dba,select_catalog_role etc., Creating a role:

Syn:- create role rolename; Ex:- create role abc;

Granting privileges to role:

Syn:- grant create session to abc;

Revoking: Syn:- revoke create session from abc;

Dictionary views: dba_roles is used to view total roles information in a database. dba_role_privs is used to know which roles are assigned to users. session_roles is used to view the roles for a particular session. role_role_privs is used to view which roles are assigned to roles. role_tab_privs is used to view which roles are assigned on tables (or) colums.

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DBA NOTES role_sys_privs is used to know the privileges of roles. user_application_roles v$pwfile_users A privilege is effected immediated after granting. But a role is effected only when we connects to that session. There is another way to activate role Sql> set_role connect;

QUOTA:Quota is some reserved space on tablespaces. This means to limit how much space a user uses on a tablespace. Quota can be assigned to user at the time of creation (or) after the creation 1) create user abc quota 10m on system; 2) alter user kittu quota 10m on system; 3) deleting quota alter user kittu quota 0m on system; dictionary views: dba_ts_quotas is used to know the how much quota is reserved for a particular tablespace. user_ts_quotas PROFILES Profile is a set of limits on database resources. Profiles are used to manage the resources of database. By default, a profile named default is available in the database. If we assign profile to user, that user cannot exceed these limits. To enable resource limits dynamically we need to set resource_limit parameter to true.  Alter system set resource_limit=true To see this parameter Show parameter resource_limit To view profile information Select * from DBA_PROFILES; Profile, resource, resource_name, limit Actually profiles has 2 types of parameters. 1) resource parameters Can be viewed by user_resource_limit view 2) password parameters Can be viewed by user_password_limits  To create profile,we must have create profile system privilege Syn:- create profile abc limit sessions_per_user 2 Idle_time 30 Connect_time 10 Failed_login_attempts

2;

 How to alter a profile

Syn:- alter profile abc limit idle_time 10;

 How to drop a profile Page 45 of 102

DBA NOTES Syn:- drop profile abc cascade;

 How to assign profile to user Syn:-alter user kittu profile abc;

Resource parameters Composite _limit Session_per_user Idle_time Connect_time Cpu_per_session Cpu_per_call Logical_reads_per_session Logical_reads_per_call Private_sga

password parameters failed_login_attempts password_life_time password_reuse_max password_verify_function password_lock_time password_grace_times

Unlimited: When a resource parameter specified with this, it indicates that a user assigned this profile can use an unlimited amount of this resource when specified with password parameter, unlimited indicates that no limit has been set for the parameter. Sessions_per_user: It specifies no.of concurrent multiple sessions allowed per user Connect_time: It specifies the allowable connect time per session in minutes. Idle_time: It specifies allowed continuous idle time before user is disconnected in minutes. Failed_login_attempts: The no.of failed attempts to log into the user account before the account is locked

ORACLE MANAGED FILES When oracle itself creates files, that files are said to be oracle managed files. There is no need to define locations and names of CRD files. The problem with OMF is only naming convention. Creating database using OMF:For this we need to add 2 parameters in init.ora They are DB_CREATE_FILE_DEST DB_CREATE_ONLINE_LOG_DEST In init.ora:Db_name=kittu Shared_pool_size=100m Db_cache_size=100m Log_buffer=32768 Compatible=10.2.0.1.0

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DBA NOTES Undo_management=auto Db_create_file_dest= ‘/oraAPP/kittu/database1’; Db_create_online_log_dest_1=’/oraAPP/kittu/database’; connect as sys as sysdba  startup nomount Then database is created with creating a directory with database name. in that 3 directories are created ., They are Datafile in this all the data files are stored Online log in this , log files are created Control file in this control files are created SYSTEM tablespace with datafile is created with 200mb size and is auto Extensible. SYSAUX tablespace with data file is created with 100mb size and is auto extensible UNDo tablespaces named SYS_undots is created with 120 mb size and is Auto entensible. 2 redo log groups are created each one with size 100mb .each one contains Only one member. it creates one control file.

*In 10g, we can mention more than one destination parameter for redo logs DB_CREATE_ONLINE_LOG_DEST_1 DB_CREATE_ONLINE_LOG_DEST_2

In this case we mention in init.ora as DB_CREATE_FILE_DEST=’/oraApp/db1’ DB_CREATE_ONLINE_LOG_DEST_1=’/oraAPP/db1’ DB_CREATE_ONLINE_LOG_DEST_2=’/oraAPP/db2’

Now datafile is created in db1 Two control files are created in db1 and db2  Two redolog groups are created in db1 and db2 Each group contains 2 members The control file in 1st dest location is primary one In pfile indicates for all instances . either we use this RAC instances. After creation of database, we need to specify control files location in init .ora i.e., control_ files=/oraAPP//db1/kittu/controlfile/a1_ctr.ctl then only the control file is opened. if we don’t mention undo_management is in manual mode, we can’t assign undo_tablespace to database Drop database: Sql> startup mount Sql>alter system enable restricted session; Sql>drop database when we drop database, all the physical structure of database. Page 47 of 102

DBA NOTES when we create any tablespace, datafile, logfiles. Then a directory with database name as a name is created in db1/kittu/kittu. In this again three directories are created 1)datafile 2) online log 3) control file All the files we created after the creation of database, will be stored in this locations The users related datafiles and redo’s created after execution of database will be stored in these directories.  Note that OMF default size is 100mb, and the file size can be overridden at any time. You can specify the filesize only bypass OMF and specify filename and location in datafile clause.  Oracle enhanced the oracle 9i alter log to display message about tablespace creation and data file creation. To see the alert_log, you must go to background_dump destination directory.  show parameter background_dump  The parameter db_recovery_file_dest defines the location of flash recovery area, which is default file system directory (or) ASM disk group where database creates RMAN backups, when no format option is used, archived logs when no other local destination is configured and flashback logs. Create tablespace:Create tablespace ts01;

It alone creates datafile of size 100mb Adding a file to tablespace:Alter tablespace add datafile; (or) Alter tablespace ts01 add datafile ‘--path--‘ size 10m;

 Drop a tablespace:Drop tablespace ts01;

creating log group:Alter database add logfile group3; Alter database add logfile member ‘------‘ to group3;

log member:-

Alter database drop logfile group3;

Uses:1) 2) 3) 4)

they make the administration of database easier. They reduce corruption caused by administrators specifying wrong file. They reduce wasted disk space consumed by absolute files. They simplify the creation of test and development database.

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DBA NOTES

PARAMETER MANAGEMENT when we want to change database architecture, then we use alter Database command when we want to change parameter to specific session (user), we use Alter session command when we want to change parameters to entire database, use alter System command parameters are 2 types Dynamic parameter The parameters whose values can be modifiable dynamically at Run time. Static parameters The parameters whose values cannot be modifiable at run time We can change in init.ora Static parameters are 2 types 1)tunable parameters:-

Parameters whose values can be modifiable in init.ora . for Effecting these values, we need to bounce the database. Ex:- db_file Db_processes 2)non_tunable parameters: Parameters whose values cannot be modifiable at any Situation To know parameter information:v$parameter To know whether the parameter is modified for only session and for entire database. Select name isses_modifiable, issys_modifiable from v$parameter.

Alter command:

Alter system/session set parameter_name= [spfile/memory/both]

Spfile it stores only in spfile MemoryIt stores only in memory(database) It erases when we bounce the database Both both in memory and spfile default Ex:-alter system set db_cache_size=100m scope=both;  strings –a spfilekittu.ora/ grep log_archive It shows log_archive in text format.

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DBA NOTES

MANAGING INVENTORY Inventory means storage  oracle inventory is the repository(directory) which stores/records oracle software products and their oracle_home location on a machine. This inventory now a days in XML format and called as XML inventory where As in past it used to be in binary format called as binary inventory.  there are basically 2 types of inventories. 1) local inventory:- it is also called oracle home inventory, inventory inside each oracle home is called as oracle_home inventory (or) local inventory. This inventory holds information to that oracle home only. Location: oraclehome/inventory 2) global inventory:- it is also called as central inventory. It holds the information about the oracle homes installed on that server. It contains homes installed on that server. It contains homes, locations like Home_name=”ramu” loc=”/oraAPP/kittu” type= “o” idx=”1”/ This global inventory location will be determined by file orainst.loc. It is in /etc[linux] and /var/opt/orace[solarises] . It contains Inventory_loc=/etc/inventory If we want to see list of oracle products on machine check for file inventory.xml:Location:- /etc/oraInventory/contents XML/ Can we have multiple global inventories on machine? Yes, you can have multiple global inventory but if you are upgrading (or) applying patch then change inventory pointer oraInst.loc to respective location. What to do if my global inventory is corrupted? No need worry if our global inventory on machine using OUI and attach already installed oracle home by option attach home ./runInstallersilentattachhomeinvptvloc $location_to_oraInst.loc ORACLE_HOME=”oracle_home_location” ORACLE_HOME_NAME=”oracle_home_name” Cluster_nodes=”{}’

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DBA NOTES

ORACLE NETWORKING Actually in real time environment, we provide database, to client as a non_local connection. Non_local connection means connecting to database server through softwares like sqlplus, OEM,VB,.NET,JAVA from client system. There are some softwares called net80, oracle net for configuring tns entry in client system. They came with oracle installation. for java,jdbc is used to connect to oracle for .net,odbc is used to connect to oracle oracle connectivity components are toad, sqlplus,oem etc, sqlplus is software which comes with oracle to connect to database. It is cebbased technology. To access the database from client system, we had to following the following steps:Step1:- server side We need to configure listener on the server listener is a utility which is listening to database connections It is an executable file Its location is ORACLE_HOME/network/admin/listener.ora In one server we may have more than one listener depending on the load (no of clients communication to the server)  Next open listener.ora file. It is readable text file. It is reachable text file  $ vi listener.ora LISTENER_NAME = (ADDRESS_LIST= (ADDRESS=(PROTOCOL=IPC)(KEY=EXPROC LISTENER NAME)) (ADDRESS=(PROTOCOL=TCP)(HOST=192.168.0.207)(PORT=1521)) ) SID-LIST_LISTERNAME= (SID_LIST= (SID_DESC= (ORACLE_HOME=/oradb/nani9i) (SID_NAME=databasename) ) (SID_DESC= (SID_NAME=PLSEXTPROC) (ORACLE_HOME=/oradb/nani9i) (PROGRAM=extproc) ) )

While defining listener, we provide

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DBA NOTES Listener name List of sid’s (database) Protocol (tcp/ip) Port number (default 1521) We must have different port numbers for different listener.  Host name (ip address)    

After configuring listener in listener.ora open the database and exit and follow below commands $lsnrctl start -- it will start all the listener in listener.ora $lsnrctl start kittu -- it will start listener kittu Lsnrctl is an executable which is in ORACLE_HOME/bin Step2: client side  Install oracle network, protocol adapter for tcp/ip (client side components)  We need to configure tns entry to connect to database through a listener  We use sqlplus, toad, oem , isqlplus as the front end to connect to database.  For configuring tnsentry,we have to know the ORACLE SOFTWARE home in client system  We need to configure tnsentry in tnsnames.ora file present in home /oracle/orad2k/network/admin/tnsnames.ora  For sqlplus, we find this by right clicking and select properties and find the home.  In Toad there are multiple homes we know the home by opening the toad. We can set toad home by clicking sql .net configuration help selecting the corresponding home ad click on set as toad home button. Then find the location of tnsnames.ora and configure it.  We need to define an alias in home  While defining alias provide 1) Alias name(tns name (or) entry) 2) Target server name (or ip address) 3) Target sid (database_name) 4) Protocol (tcp) 5) Target port number(defined in listener.ora)  After defining the alias, we check using C:\tnsping (tns ping utility for oracle, where as ping is utility for tcp/ip) Tnsnames.ora Tnsentryname = (description = (ADDRESS=(PROTOCOL=TCP)(HOST=TARGET SERVER)(PORT=1521) (CONECT_DATA=

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DBA NOTES Step 3: Now we can connect to database through sqlplus (or) oem or toad  open sqlplus or toad Sqlplus username kittu [username in database] Password xxxx Host xhni [tnsname]

OR Username kittu/xxxx@xhni Toad Username (or) databasename Schema Password

chinni kittu ram

(tnsname)

Then click on ok button Now we can acess to database To know whether the listener is started or not:$pd –ef | grep tns Stop listener: $listener stop kittu -- command completed successfully What happens when a Service “instance name’ has 1 instance (s) instance “dba”. Status unknown has handler for this service. The command completed successfully  One listener can have multiple service handlers for one or more instances i.e one listener for multiple databases in tnsnames.ora we define 2 tns entries with same port but with different sids dba1 dba2 listener clients apple=(ADDRESS_LIST =(ADDRESS=(PROTOCOL=IPC) (KEY=EXTPROCapple(ADDRESS =(PROTOCOL=TCP) (HOST=192.168.0.207(PORT=1599))) SID_LIST_apple=(SID_LIST=(SID_DESC=(ORACLE_HOME=/home) (SID_NAME=db9i)) (SID_DESC=(O_H=/tmp)  In case of with different port numbers  we can define multiple listeners for one database Page 53 of 102

DBA NOTES  in tsnames.ora we defined, multiple tns enter with different port numbers and same sid Everything will be same, only we has to create and listener with different port numbers Tip  using lsnrctl command we can 1) Start 2) Stop 3) Services  to know the services of server dedicated or mts or local or nonlocal 4) Debug 5) Status 6) Help 7) Reload  it will restart listener  listener can be started regardless the status of instance.  if we want to ……….. We need to define TNS_ADMIN environment variable in bash-profile Export TNS_ADMIN =/home Then oracle will look for listener.ora in /home directory  tnsnames.ora file can have ‘n’ number of tns entries  There is no significance of tns entry name we can give any name Trc_level admin SESSION MANAGEMENT  We can know the each sessions information from v$session view  The commonly used columns in v$session are Sid, serial#, username, logon_time, status  In v$session there is no username for background process  By using sid amd serial# we cam kill a session To know own session id(statistics) Select sid,serial# from v$mystat where rownum=1; To kill a session Syntax: - alter system session ‘sid,serial#’; Ex: alter system kill session ‘1,20’; STORAGE MANAGEMENT we know that the data stored in datafiles. Audit the finest level granularity oracle database stores data in data blocks also called logical block, oracle blocks or pages)

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DBA NOTES

Segement: A segment is a set of extents that contains all the data, for a specific logical storage structure with a tablespace For example, for each table, oracle database allocates one or more extents to form the tables data segement. Extent: An extent is a specific number of contigous data blocks that are allocated for storing a specific type of information Oracle Block: A block a smallest unit of storage in Oracle the size of a datanlock is fixed when the database is created and cannot be changed except by rebuilding the database from . This is primary data block sizes of datablocks are 2k,4k,8k,10k,32k The size of block is determined by the parameter db_block_size in init.ora file.  In o/s also name stored in blocks only o/s file blocks only o/s file blocks size is 512 bytes or 1k  When we try to read some data oracle uses db_blocks. Oracle will retranslating while reading data.  In 10g default blocksize is 8k In 9i, default blocksize is 2k  when we define datafile size as 8m actually 1m datafile as it block size is 8k contains 130 blocks

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DBA NOTES

DATA BLOCK STRUCTURE Block header Table directory Row directory Free space Row data Or Used space Block header: It contains general block info such as the block address and the type of segment (table or indexes) Table directory:- This portion of datafiles contain information about the tables having rows in the blocks. Row directory:- This portion of data block contains info about the actual rows in block (including address of each row piece in the row data area). After the apce has been allocated in the row chaining of a data block overhead this space is not reclaimed when the row is deleted therefore, a database that is currently empty but had up to 50 rows at one time continous to have 100 bytes allocated in the header of row directory oracle databases reuses this space only when new rows are inserted in the blocks. Overhead: The data blocks header table directory and row directory are referred to collectively as overhead some block overhead is fixed in size. The total block overhead size is variable. On average the fixed and variable portions of data block overhead total 84 to 107 bytes. Rowdata: This portion of data block contains table or index data. Row can space blocks. FreeSpace: Free space is allocated for insertion of new rows and updates to rows that require addition. Pctused: This parameter sets the minimum percentage of a block that can be used for row data plus overhead before new rows are added to that block before new row are added to that block, after a block is filled to the limit determine by pctfree, oracle database consider the block unavailable for the insertion of new rows until the percentage of that block falls beneath the parameter pctused until the value is achieved, oracle database uses the free spaces of the data block only for updates to rows already contains in the data block.

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DBA NOTES For example:- pctused 40 In this case a data block used for this tables data segments is considered unavailable tables data segments is considered unavailable for the insertion of any new rows until the amount of used space in the block falls to 89% or less. Init trans: This parameter specifies how many transactions can be accessed to the dbblock at any point of particular time Freelists : this parameter is used in rac: Tip: once the primary block size is mentioned you can create new tablespace with alternate block size for creating table with parameters. Syntax:-

create table abc(a number) Pctfree 10 , pctused 30, initrans 10;

To obtain object level parameters information:Select table_name,pct_free,pct_used,init_trans,max_trans from dba_tables where table_name=’abc’;

By default :- pctfree-10,pctused-40,initrans-1,max_trans 255 If we specify parameters pctfree - 10, pctused -30, inittrans-30, max_trans -255 Extent Management An extent is an uninterrupted or contiguous allocation of blocks within a segment. Extents are assigned to a segment automatically by oracle. Oracle will allocate anything in the form of extents. An extent must be an contiguous blocks within a single datafile, so an extent cannot span multiple datafiles. Oracle will allocate the size of extents based on type of tablespace. When we create a table, oracle database allocates a segment and a initial extent of a specified number of data blocks. The size of extent is determined by storage parameter. These parameters are also called as object level parameter Storage Parameters: • INITIAL • NEXT • MINEXTENTS • MAXEXTENTS • PCTINCREASE INITIAL: The parameter specifies the first extent and the size of extent NEXT: If the datablocks of a segment initial extent became full and more space is required to hold new data oracle database automatically allocates an incremental extent Page 57 of 102

DBA NOTES for that segment. The size of incremental extent is same or greater than the previously allocated extent i.e, we specify the extent after initial extent through this parameter. MINEXTENT: This parameter specifies the total number of extents to be allocates when we create a (table (segement) or index) MAXEXTENT: This parameter specifies the up to how many extents a segment can hold. PCTINCREASE: This parameter specifies the incremental percentage of extent that is to be created after the NEXT EXTENT. By default its value is 50%. For example consider a) Initial 1m Next 1m Minextents 1 Maxextenst 4 Pctincrease 50% 1m b) Initial Next Minextents Maxextenst Pctincrease 1m

1m

1.5M

2.25M

3.375M

1m

1.2m

1.5m

1m 1m 2 5 20% 1m

If we don’t specify storage parameters for a extent. Oracle itself allocates the default storage parameters. Segment is creation of extents. Segment name is nothing but as object name. when we create a table or index it creates segment. By default each extent contains max of 5 blocks and min of 2 blocks.

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DBA NOTES Create a tablespace and segment find the storage parameters without specifying them? Sql> Sql> Sql> Sql>

create tablespace tbs datafile “ alter user kittu identified by kittu; conn kittu/kittu create table ram(a munber);

“

10m;

We can archive the extents information from dba_extents and dba_segments. Sql> select initial_extent, next_extent, max_extent, min_extent, pct_increase, blocks, bytes from dba_segments where segment_name=’ram’; Sql> save sess.sql

All the parameters, blocks and their size for extents are allocated as per operating system. Create a table in the tablespace with some parameters and check the parameters? Sql> create table chinni(a number) Storage (initial 1m nect 1m minextents 1 pctincrease 100%); Sql> @sess.sql

maxextents 5

Now also maxextents will be taken as o/s specific When database having db_block_size as 8k If we define extent size as 1m Then each extent holds 128 blocks Q) How can we determine table or index size from dba_extenst or dba_segments?  Select segment_name,bytes from dba_extents where segment_name=’RAM’’;

OR Select segment_name,bytes from dba_segments where segment_name=’RAM’;

Extent Management A tablespace is a logical storage unit. Why are we saying a tablespace is not visible in the file system. oracle store data physically in datafile. How to create tablespace? Create tablespace ts_name Datafile ‘………….’ Size 2m

Minimum extents (this ensures that every used extent size in the tbs is a multiple of integer) Blocksize Page 59 of 102

DBA NOTES Logging: By default tbs have all changes written redo No logging: Tbs do not have changes written redo Online: Tablespace is online i.e available Offline: Tablespace unavailable immediately after creation Permanent: Tablespace can be used to hold permanent object. Temporary: Tablespace can hold temp data Extent Management is of two types a) Dictionary Extent Management b)Locally Extent management The tablespace are maintained in dictionary extent management is dictionary managed tablespace. The tablespace which are maintained in local extent management is called locally managed tablespace. Locally managed tablespace: The extents are managed with in tablespace in locally managed tablespaces all the tablespace information and extent information is stored in datafile header of that tablespace and don’t use data dictionary table for storing information. Advantage of LMTS is that no DML generate and reduce contention on data dictionary tables and no undo generated when space allocation or deallocation occurs. The storage parameters NEXT, PCTINCRESE, MINEXTENTS, MAXEXTENTS, and default STORAGE are not valid for segments stored in LMTS. To create a locally managed tablespace,you specify local in extent management clause of create tablespace statement. We have 2 options for lmts: 1) system or auto allocate 2) uniform q) how to create lmts create tablespace tbs datafile ‘star.dbf’ size 10m extent management local; SYSTEM (or) AUTOALLOCATE: Autoallocate specifies that extent size are system managed oracle will choose “optimal” next extent sizes starting with 64kb as the segment grown larger extent size will increase to 1mn,8mb and eventually to 64mb .This is recommended only for a low or unmanaged environment. Default autoallocate i.e it takes database default storage. Parameter Syntax:create tablespace tbs datafile ‘star.dbf’ size 10m extent management local autoallocate;

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DBA NOTES UNIFORM: It specifies that the tbs is managed with uniform extents of size bytes. The default size is 1m . The uniform extent size of lmts cannot be over written when a scheme object such as table or index created Syntax: -

create tablespace tbs Datafile ‘/oraapps/star.dbf’ size 10m Extent management local uniform size 128k;

Dictionary Managed Tablespace: When we are declaring tablespace as dictionary managed tablespace, the data dictionary manages the extents. The oracle server updates the appropriate tables(sys.fet$ and sys.uet$) in the data dictionary whatever an extent is allocated or deallocated. Syntax: -

create tablespace tbs Datafile ‘har1.dbf’ size 10m Extent management dictionary Default storage(initial 1m next 1m minextent 2 maxextents 121 pctincrease 0)

We can alter all parameters except initial and minextents in dmts i.e if we create dmts then extent info is stored in dictionary and real data is stored in datafile of that tablespace. In that case we need more I/O i.e the oracle has to search for extents in dictionary. which degrades the performance. In oracle 8i > only dmt available From 9i> both dmt and lmt (default) From 10g> both dmt and lmt (default) SEGEMENT Segments are the storage objects within the oracle database. A segment might be table, an index, a cluster etc. The level of logical database storage above an extent is called segment. A segment is a set of extents that contains all the data for a specific logical storage structure within a tablespace. For example for each table oracle database allocates one or more extents to form that tables data segment and for each index, oracle database allocates one or more extents to form its index segment There are 11types of segments in oracle • table • table partition • index • index partition

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DBA NOTES • • • • • •

rollback deferred rollback lobindex temporary cache permanent

These types can be grouped into four segment • data segment • index segment • rollback segment • temporary data segment Data Segments: A single data segment in a oracle database holds all of the data for one of the follow.. • A table that is partitioned or clustered • A partition of partitioned table • A cluster of table. Oracle database creates the data segment when you create the table or cluster with create statement. The storage parameters for a table cluster determine how its segments extents are allocated you can set there storage parameters directly with appropriate create or alter the efficiency of data retrieval and storage for data segment associated with the object. Index Segment: Oracle database creates the index segment for an index or an index partition when you issue the create index statement. In this statement we can specify storage parameters for creation of index. The segments of table and index allocated with it do not have to occupy the same tablespace setting the storage parameters directly affect the efficiency of data retrieval and storage. Temporary segments: When processing queries oracle database often requires temporary workspace for intermediate stages of sql statement parsing and execution oracle database automatically allocates this disk space called a temporary segment. Typically oracle database requires a temporary segment as a database area for sorting. Undo segments: Oracle database maintains information to reverse changes made to the database. This information consists of search of the action of transactions, collectively known as Undo .undo is stored in undo segments in an undo tablespace.

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DBA NOTES

How extents are allocated: Oracle database uses different algorithms to allocate extents, depending on whether they are locally managed or dictionary managed. With LMTS, oracle database looks for free space to allocate to a new extent by first determing a candidate datafile in a tbs and the search the datafiles bitmap for the required number. When extents are allocated: In general the extents of a segment do not return to the tablespace until you drop the schema object where data is stored in the segement. A dba can deallocate the unused extent using the following sql Syntax: Alter table table_name deallocate unused ; Periodically, oracle database modifies the bitmap of the datafile(for lmts) or update the data dictionary (for dmts) to reflect the regained extents as available space An data in the blocks of freed extents becomes inaccessible. Periodically oracle database deallocates one or more extents of a rollback segment if it has optimal size specified. If the rollback segment in larger than optimal (i.e it has too many extents) the oracle database automatically deallocates one or more extents from rollback segment. How temporary segments are allocated? Oracle database allocates temporary segments differently for queries and temporary tables. SEGMENT SPACE MANAGEMENT Oracle allocates space for segments in extents. When existing extents of segment are full ORACLE allocates another extent for that segment. Because extents are allocated are needed, the extents of a segment may or my not be contigous on disk, and may or may not span files. Segment header is stored in the first block of the first extent There are 2 choices for segment space management a)manual b)auto Manual: This option uses free lists for manging free spaces with in segments. Create tablespace tbs Datafile kit.dbf size 10m Segment space management manaual;

Auto : This option uses free lists for manging free space within segments. This is typically called automatic segment space management it is default. Page 63 of 102

DBA NOTES

Freelists: Freelists are lists of data blocks that have space available for inserting • • • • • •

Even datafile must consist of one or more o/d blocks. Each o/s block may belongs to one and only datafile. Every Tablespace may contain one or more segments. Each segment must exist in one and only one tablespace. Every segment must consist of one or more extents. Each extent must belong to one and only extent. Every extent must consist of one or more oracle blocks. Each oracle block may belong to one and only one extent. Every extent must be located in one and only one datafile.The Space in datafile may be allocated as one or more extents Every oracle block must consist of one or more o/s blocks.Every o/s block may be part of one and only one oracle block.

How to convert between LMT AND DMT? The DBMS_SPACE_ADMIN packages allows DBA’s to quickly and easily convert between LMT AND DMT mode Sql> exec dbms_space_admin.tablespace_migrate_to_local(‘ts’); Sql> exec dbms_space_admin.tablespace_migrate_form_local(‘ts’);

Create a tablespace without any option of extent management and create a table amd check? Create tablespace tbs Datafile

‘aa.dbs’

size 4m

Obs: Extent_managment=local Allocation_type=system Segement_space_managment=auto Initial = 65536 Min_extent=1 Max_extent= 2147483645 Bytes =65536 The extents are allocated by o/s specific, by default it takes EM as local  grant dba to hari identified by hari  alter user hari default tablespace tbs;  comm. hari/hari create table a (a number);

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DBA NOTES select segement_name, initial_extent, next_extent, min _extent, max_extent, pct_increase, allocation_type, extents, bytes where segment_name=’A’;

bytes will display size of extents allocated extents will display how many extents are allocated  create a table with storage parameter create table abd(a number) storage (initial 1m,next 1m,minextents 1,maxextents 3,pctincrease 20);

it takes all values default but only minextent size different  create LMTS with autoallocate and check:create tablespace tbs datafile ‘/oradb/………..’ size 5m extent management local auto allocate;  default system allocation_type to check allocation_type

select tablespace_name, allocation_type from dba_tablespaces;

allocation_type is system Create LMTS with uniform amd check Create tablespace ts04 datafile ‘ts04.dbf’ size 3m extent management local uniform 128k. -

create table without mentioning parameters create table a (a number) storage(initial 1m next 1m minextents 2 maxextents 4);

initial takes 2m But while storing it takes extent sizes as uniform Allocation type – Manual Create DMTS with no parameter and create table Create tablespace ts05 datafile ‘ts05.dbf’ size 5m extent management dictionary;

Obs:- initial – 40960, next 40960, min – 1 , max – 505 , E.M – Dictionary, pct -50, S.S.N – Manual , Allocation type – User - When we create table with out parameter same values are effected - create table a2 (a number)

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DBA NOTES storage(initial 1m next 1m minextents 1 maxextents 5 pctincrease 50); - All the values as mentioned per parameters are effected. - we can alter storage param values except initial and minextents. Create DMTS with storage parameters Create tablespace ts07 datafile ‘ts07.dbf’ size 10m dictionary management dictionary default storage(initial 1m next 2m minextents 2 maxextents 5);

Note – all the above values are assigned to parameter; Segments space management Create DMTS without mentioning S.S.P: Create tablespace ts08 datafile ‘ts08.dbf’ size 1m extent management dictionary;

Default S.S.P is manual for DMTS. We can change DMTS to LMTS id S.S.P is manual. exec dbms_space_admin.tablespace_migrate_to_local(‘ts08,dbf’);

No auto S.S.P is valid with D.E.M Create LMTS without mentioning S.S.P: Create tablespace loc datafile ‘loc.dbf’ size 3m; Default SSP is auto for LMTS. In this case we can change LMTS to DMTS. So first convert SSP from auto to manual, it is not possible. So create tablespace with SSP as manual. Create tablespace s01 datafile ‘s01.dbf’ size 5m;  exec.dbms_space_admin. tablespace_migrate_from_local(‘s01’); Now it will be migrated from local to dictionary Ie., we can chage LMTS to DMTS when ssp is manual • the allocation type for DM is user • to know the source code of tablespace select dbms_metadata,get_dd1(‘TABLESPACE’,’LOC’,from dual); dbms_metadata and dbms_space_admin are packages ROW CHAINING & ROW MIGRATION If you notice poor performance in your oracle database row chaning and migration may be one of several reasons, but we can present some of them by properly designing and / or diagnosing the database. Row migration & Row chaning are two potential problems that can be prevented by suitable diagnosing, we can improve database performance. The main considerations are: what is row chaining & row migration? Page 66 of 102

DBA NOTES  how to identify row migration & chaining?  how to avoid row migration & row chaining? Row Migration: We will migrate a row when an update to that row would came it to now fit on the block anymore (with all the data that exists there currently in that row) A migration means that entire row will move and we just leave behind the forwarding address. So, the original block (old block) has the row id of the new block and the entire row is moved. In this we need more IO Row Chaining: A row is too large to fit into a single database block for example, if you use a 4kb blocksize for your database, and you need to insert a row of 8kb into it, oracle will use 3 blocks and store the row in pieces. Some Conditions that will cause row chaining are • Tables whose row size exceeds the blocksize • Tables with LONG and LONG RAW columns are prone to having changed rows • Tables with more than 255 columnds will have chained rows as oracle break wide tables up in to pieces. So, Instead of just having a forwarding address on one block and the data on another we have data on two or more blocks • Insert and updata statements that came migration and chaning perform poorly, because they perform additional processing. • Selects that use an index to select migrated or chained rows must perform additional I/O Detection: Migrated and chained is a table or cluster can be identified by using the analyze command with the list chained rows option. This command collects information about each migrated or chained row and places this information into a specified output table. To create a table that holds the chained rows, execute script utlchain.sql. SQL> ANALYZE TABLE scott emp LIST CHAINED ROWS; SQL> select * from chained_rows;

Resolving:  In most cases, chaining is unavoidable, especially when this involves tables with large columns such al LONG, LOBs etc., when you have a lot of chained rows in different tables and the average row length of the tables is not that large, then you might consider rebuilding the database with a larger block size. Ex:- you have a database with a 2k block size different tables have multiple large varchar columns with an average row length of more than 2k. Then this means that you will have a lot of chained rows because your block size is too small rebuilding the db with a larger block size can give you a significant performance.

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DBA NOTES Migration is caused by PCTFREE, being set too low, there is no enough room in the block for updates. To avoid migration all tables that are updated should have there PCTFREE set so that there is enough space within the block for updates. You need to increase PCTFREE to avoid migrated rows. If you leave more space available in the block for updates, then the row will be having more room to grow. 1) Update set column=value where 2) Alter table add column datatype 3) Alter table modify column datatype 4) Create view as select col1,col2 from 5) Create index on tablename(column) 6) Create sequence increment by 1 7) Drop index 8) Drop view 9) Drop table 10) Drop sequence 11) Create synonym for object 12) Drop synonym

 In OS level :SQL level : In OS level :SQL level : SQL level :-

vmstat, iostat v$version getconf LONG_BIT platform_wave from v$datafile address from v$sql

DB-START AND DB-SHUT  There are 2 built in commands provided by oracle which are used to start and shut down the data base  We use this activity in Emergency Maintainence DB-START: This is a script which is located in ORACLE_HOME/bin. This is an executable file when we execute this file. It will start the Oracle database from /etc/rcl..locs. It should be only executed asa part of system boot procedure. This script will start all the databases listed in the ORATAB file whose third field is ‘Y’. This field is laos referred as monitoring field.There is no need to pass any arguments. This script will ignore he entries where first field is ‘X’. In ORATAB:- $ORACLE_SID: $ORACLE_HOME: Eg:- kittu: /oraDB/kittu:Y DB-SHUT: This is an executable file which is located in $ORACLE_HOME/bin. This will shutdown the database whose third field is Y.

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DBA NOTES  When we run there scripts for first time. It creates 2 logfiles in ORACLE_HOME ->startup.log ->shutdown.log  When we start and shutdown the database startup and shutdown information will be updated into these files

BACKUPS Backup and recovery is one of the most important aspects of DBA’s life. If you love your company’s data, you would very well love your job. Hardware and software always be replaced but your data may be irreplaceable.  Backup: is taking the copy of data in some other location.  Restoration means copying backup files from backup. Storage area in Hard disk, Tape, CDs, Pendrive etc., to Original location.  Recovery is the process of applying redologs to the database to roll it forward. (or) Applying Archieve log files to the database to get the data after the backup is taken. Oracle has its own Backup Methods -Physical -Logical Physical Backup:- means making the copies of the files related to physical architecture. Eg: Datafiles, Control files, Redolog files Logical Backup:- means taking the copies of logical structure of Database. Eg: Tables, Schemas, Tablespaces, Database  In real time , all backup are run as root (maximum)  There are also third party backup technologies available one of them and the most fastest is VERITAS We will be integrating the veritas software & hardware with the database. There must be a separate admin (veritas admin) to maintain this technology. Minimum it backups terabytes data just in one hour only!!  In real time environment we use tar command to take the backup into tape. $ tar cvf filename * WHOLE BACKUPS:

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DBA NOTES A whole backup is a backup of all the datafiles, control file and ( if u are using it) the spfile. Remember that as all multiplexed copies of the control file are identical , it is necessary to backup only one of them. You do not backup the online redologs. Online Redolog files are provided by multiplexing and optionally by archiving. Also note that only datafiles for permanent tablespaces can be backed up. The temp files used for your temporary tablespaces cant be backed up by RMAN or can they be put into backup mode for an OS backup. PARTIAL BACKUP: It will include one or more datafiles and control file. It is copy of just a part of the database. INCREMENTAL BACKUP: A incremental backup is a backup of just some of blocks of datafile. Only the blocks of that have been changed or added since the last full backup will be included. It is done by RMAN ONLINE BACKUP: Backup which is taken when the database is up or running. OFFLINE BACKUP: Backup which is taken when the database is shutdown. PHYSICAL BACKUP Traditional  RMAN Cold  Cold Hot  Hot COLD BACKUP Backup which is taken when the database is down is said to be cold backup. Steps to perform the Cold backup: 1) List out the datafiles, Control files and Redolog files by using v$datafile, v$datafile, v$logfile. Sql> select name from v$datafile; Sql> select member from v$logfile; Sql> select name from v$controlfile;

2) Shut down the database with shut immediate option. Sql> shut immediate;

3) Now copy the crd files to backup location in OS level. $cp /oraAPP/app/* /backup/ How can we check whether the cold backup is working properly or not?

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DBA NOTES       

shutdown the database copy crd files start the database create a user and some folder in it. Remove crd files in OS level Resore from backup location (files must be restored exactly to same location) Start database and check the database for mewly created users and tables. [thwy will not exit,coz you restore the database from old backup]

How do we automate the cold backup? By writing a shell script and submitting it to cron, we can automate hold backup . Cron should be scheduled as root. SHELL SCRIPT for Cold Backup: # !/bin/bash ------------- this indicates to execute this code in bash shell ############################################################### ## Name : cold.sh ## ## Description: This files takes cold backups of crd files ## ## Date: 13.6.08 ## ## Author: Ramesh ## ################################################################ # Set the environment Export ORACLE_SID=dbkittu Export ORACLE_HOME= /oraDB/chinni Export PATH=$PATH:$ORACLE_HOME/bin #SHUT DOWM THE DATABASE SQLPLUS select filename,tablesapce_name from dba_data_files;

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DBA NOTES For each tablespace: Put tablespace in hot backup mode(begin backup mode) Sql>alter tablespace system begin backup

Copy each datafile of that tablespace To backup location Sql>cp /oraAPP/kittu/system.dbf

/stage/backup/.

Put tablespace in end backup mode. sql>alter tablespace system end backup;

backup the control file.

Sql>alter database backup controlfile tp ‘/stage/backup/c1.ctl’

Conform all table spaces returned to normal mode. Sql>select file # ,status ,change#,time from v$backup where status!=’Not Active’;

Perform an archive log switch: Sql>alter system switch logfile;

Or

Sql>alter system archive log current;

Backup archive redo log file: What happens when we put tablespace in begin backup mode? Sql>alter tablespace system begin backup;

The below process os going on when ew issue the archive command. Oracle has it all under control Remember that every time oracle datafile has an scn. That is changed every time when an update is made to a datafile. Also remember that every time oracle makes a change to a datafile it records that changes in the redolog. When a tablespace is in being backup mode the following steps occur: Oracle check points the tablespace (ie a check point is occurred for the tablespace) now all changes om db_cache will be flushed to datafile. Any ware updates the table (or) indexes ….. that datafile ,all the updated will be sent to datafile but at this time the scn marks for each datafile in the tablespace are frozen (blocked) at their current values. The scn markers (numbers) will not be updated until the tablespace is taken out of backip mode. ORACLE SWITCHES TO logging full images of change database to the redologs this is why the redologs grow at a mich faster rate while hot backups are going on.

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DBA NOTES ie oracle maintains full copy of changed db-blocks in the redologs .’if log sitch occurs they are archived’ at the point of time if any user wants to retrieve the updated data he gets that data from redologs. If the data in redologs gets archived then he will retrieves the data from dictionary cache where they are stored an default transactions. they stored as temporary statements. Suring hot backup the performer of the system slows sowm. When we put the tablwspafe inend backup mode the headers of datafiles get released and the scn numbers are updated using redolog files. Tablespace ckpt: A checkpoint scn occurred on onlu one ts is said to be checkpoint only that ts has differ scn compared to all ts’s this is possible where we perform Alter tablespace ts offline Alter tablespace ts begin backup. Database checkpoint: Checkpoint occurred for only database all scn’s must be synchronized at this time(ie equal). How can we automate hot backup: We can automate hot backup by writing shell script Shell script for hot backup $vi hotbackup.sh #set the environment Export oracle_sid=sree Export oracle_home=/stage/10.2.0 Export path=$path:$oracle_home/bin #make dynamic script: Sqlplus sekect checkpoint_time in v$datafile_header; Difference between scn and checkpoint Scn is representing with scn-wrap and scn-base whenever scn-base reaches 422949672909(2^32),scnwrap goes up by one and scan base will be reset to 0.the way you can have a maximum scn at 1.8e+19.

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DBA NOTES Checkpoint number is the scn number at which all the dirty buffers are written to disk. The checkpoint can be at object/tablesapces/datafiles/database level. Scn –wrap,scn-base are retrieved from table smon-scn-time Select scn-wrap,scn-base from smon-scn-time; Checkpoint number is never update for datafiles of read-only tablespaces. We can also query v$transaction to arrived at the scn for that transaction Control records information about that checkpoint and archived swquences along with the other information. q) does oracle do either crash recovery (or) transation recovery after shutdown abort if the checkpoint was taken right before the instance crash? Yes, oracle perform roll forward first if there are any changesbeyond that checkpoint and roll back any checkpoint and roll back any uncommitted transations Scn number are begin reported at frequent intervasls by smon in”smon-scn-time” table. q) when this no of highest scn will be over,then what happen will oracle restart from first number? If the scn really reached to its maximum allowed value (after exhausting all wraps),database has to be opened in reset logs mode and scn will start from beginning all over again. Q) does all the redo ectries has scn attached to them (or) does only the commit entries has? All changes recorded in the redo (including commits and rollbacks ) will hace scn associated with them. Hot backup Conditional execution for database level:

$ps-ef |grep smon|grep venkat| grep –v grep

It will show venkat-- database is up (or) down avoiding the grep statement. Hot backup script-2  set the env  check db is up or down  check who is executing the script  check db is in archive mode or not ?  generate the backup syntax using dynamic  Start backup process 1.put ts in begin backup 2.copy datafiles 3.put ts in end backup. take backup of control files to backup location.

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DBA NOTES unset the duplex dest. evlauate the size of backup. (mean source and target sizes must match)  send mail ro dba that backup in completed. Hot backup through dynamic script: name :host.sh author :kittu date :23-6-2008 purpose :the script will evaluate the state of db ad perform hot backup to local mount point #set the environment $home /bash-profile (or) export and set env variables Dbkittu #who is executing the script. Export usr=’/usr/bin/who am I’ If [[${usr} –eq “kittu”]]; Then Echo “continue operation”>> /tmp/success.ht Else Echo “exit from execution”>>/tmp/exit.lst Exit Fi

#check database is up or down Export b=’ps –ef| grep smon | grep kittu | grep –v grep| loc.l’ If [[${b} –eq l]]; Then echo “db is up …. Conformin to the next step”>>/tmp/success.lst else “db is down ------ executing “>>/tmp/fail.lst echo “dbs is down” | mail –s “db down “[email protected]. fi # check archive mode or not. Sqlplus –s conn kittu/kittu

generatew undo Sql>conn sys as sysdba

fire the below query wether the extents for rollback segments and deallocation from below rows V$rollname V$rollstat Sql>select a.name,b.writes,b.extents,b.curext,b.xacts From v$rollstat b,v$rollname a where a.user=b.user;

Usn rollback segment number Writes no of bytes of entries written to rollback segments

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DBA NOTES Xactsnumber of active transactions.

To get information about roll back segments:

Sql> select segmen_name,owner,tablespace_name,status from dba_roll_back_segs;

We can mention extents sizes for roll back segments also:-

Sql>create rollback segment rbs tablespace rbts Storage(inintal 100k next 100k minextents 20 maxextents 100);

Alter extents :-

Sql> alter rollback segments rbs storage (maxextents 120);

Shrinking:It means defragmentstion Sql>alter rollback segments rbs shrink to 100k;

Bringing rollback segments offline:

Sql>alter rollback segments rbs offline:

Dropin roll back segments: Sql>drop rollback segment rbs;

 we can also find rollback segment information from dba segment Sql> select segment_name,tablespae_name,bytes,blocks,extents from dba_segmetns where segment_type=’ROLLBACK’;

 what happen when we exit from database user? Auto commit occurs i.e, all the uncommitted transations are going to be commited.

UNDO MANAGEMENT Every oracle database must have a method to maintain information that is used to rollback, or undo changes to the database such information consists of records of actions of transactions, primarily before they are committed.  undo records are used to • •

roll back transations when a roll back statement is used recover the database.

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DBA NOTES till 8i the undo that used to generated, used to be handled rollback tablespace, which was directly managed. In case we have choose to first create a rollback tablespace, then create rollback segments and assign it to roll back tablespace.  now oracle 9i ,the new concept of undo tablespace is introduces,whioch helps in below ways: • • • •

it is logically managed. The undo segments are created by oracle itself. The number of undo segments are generated by oracle itself. The purpose of undo management and rollback segment is same The purpose of undo segments amd rollback segment is same except the creation and maintaince past.

it is not possible to use both methods in a single instance. However we can migrate for example to created undo tablespace in database that is using rollback segments and assign undo to db. And to create rollback segs in database that using undo ts (or) commented it However in both cases we must shut down and restart out database in order to effect the switch to another.  mode of undo space management : Manual: If we use the rollback segments method of managing undo space you are said to be operating in the manual undo management mode. Auto: If we use undo tablespace method, you are operating in automatic undo management mode. We usually determine this mode at instance startup using the undo-management parameter in the init file An undo tablepsace must available into which oracle will store undorecors. The default undo tablespace is created at database creation (or) an undo tablepspace can be created explicitly The parameter to be specified to create and assign an undo tablespace is undo_tablespace.  when instance startup,oracle automatically selects for use the first available undo tablespae if there is no undo tablespace available the instance starts,but uses system rollback segmet. This is not recommended. And an alert message is written to alert file.  undo_retention: Retention is period of time. it is specified in units of seconds. it cam survive system crashes ie, undo genated before an instance is crash ,is retained until its retention time has expired even across restarting the machine. Page 85 of 102

DBA NOTES When the instance is recovered undo info is returned based on current setting if undo_retention parameter. Default is undo_retention=900 default

We can change this value dynamically by using below statement. Sql> alter system set undo_retention=200;

It effects immediately.  oracle 10g guarantee undo retention When we enable this option the database never overwrite unexpired undo data ie,undo data whose age is less than undo retention period this option is disabled by default .  create a undo tablespace Sql>create undo tablespace undotbs Datafile ‘/oraAPP/undo.dbf’ size 50m;

Create a undo with retention guarantee :-

Sql>create undo tablespace undotbs datafile ‘oraAPP/undotbs’ size 100m Retention guarantee;

 alter tablespace retention guarantee or no;

Sql> alter tablespace undotbs retention guarantee/noguarente

 changing undo tablespace dynamicallyto db;

Sql>alter system set undo_tablespace=’TS_NAME’;

droping undots:

Sql>drop tablespace undotbs;

table to get information about undo data: V$unditat V$rollstat V$undostat Dba_undo_extents Dba_tablespaces Dba_rollback_segs Difference between undo and roll back segments:  rollback segments are overwritten ie, when the last extent rollback segment gets filled it enters the later uncommitted to first extent of that signet only it over writes the data in those extents. We had to create rollback segments manually it used upto 8i. undo segments maintain the uncommitted data till the retention period is reached. Even though it fills all the extents also, it maintains the data till it reaches retention period.at that time it throws an error. Ora:30036 unable to extent the segment

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DBA NOTES Oracle usually takes care of creating undo segments it is introduced in oracle 9i. To build demo tables using sql Alomg with scott user : @?/rdbms/admin/utlsampl.sql select undtsn, undblock from v$undostat;

Temporary tablespaces V$sort_usage V$temstat V$tempfile V_$sort_usage Dba_temp_file Database_properties Package: Utl_recomp_stored Sql>select file_name,tablespace_name,bytes,status from dba_temp_files;

To know which tablespace is assigned to database: Sql>select property_name,property_value from database_properties; Sql>select name from v$tempfile;

Database creation we can create db without mentioning the below parameter in initfile. Db_cache_size,shared_pool_size,log_buffer and control_files; The sizes of the above parameter are db_cache)size =48m shared_pool_size=32m log_buffer=7057408 Controlfile=control.ora Loc ‘$oracle_home/dbs/ Total sga size = 112m. How can we trace a session (user)? We want to get information that what the user is doin. For this we had to follow below process. Open 2 sessions 1) as sysdba 2) scott/tiger solutions; 1) we had to get the sid. Serial# for that session. Sql> select sid, serial#,username from v$sessions where username is not null; Sid serial# username -------------------------------------------------------------------------Page 87 of 102

DBA NOTES 27

1632

scott

2) now excute the below package to enable tracing for that session. Sql> exec dbms_system set sql_trace in session (‘27’,’1632’,true); 3) perform some activities in that session 4) now server process id for that session using below query. Sql> select p.sid from v$session s, v$process p where s.paddr=p.addr and s.sid=/s; Spid 3683 With this spid a trace file is generated for this session in udump:5) go to udump location now convert this trace file to user unserst and able format and also eliminate sys related data. [ kittu@linux1 n]$ tkprof ram_ora_3683.trc sys=no] Open this file and view what are the activities being done on that session and also performance, How can we disable tracing on a session: Sql> exec dbms_system set_sql_trace_in_session (sid,serial#,false); How to kill a session Identify the pid,serial# of that session from v$session. Sql> select sid,serial#,username from v$session;

27 1749 rama Now find the server processid for this session. Sql> select p.sid from v$session s, v$process p where s.paddr=p.addr and s.sid=27;

Sid ----9082 First kill this session using the below query in sql level; Sql> alter system kill session

’27,1749’;

Now kill this session in o/s level first find out the process for this session we already found the server process id for this session with this id, kill the session. [kithu@linux2 ~] ps –ef|grep pracle ram [kithu @linux2 ~] kill -9 9082

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DBA NOTES

ARCHIVED LOGS Q) How can we controlled the number of archiver processes? This is possible by defining a parameter named log_archive_max processes sql> alter system set log_archive_max_processes=3;

Q) how can you perform manual archiving? If your DB is in archive log mode, but don’t have automatic archival enabled. Then we can manually fill archive filled online redolog files Sql;> alter system archive log all;

Views: V$database; Sql;> select log_mode from v$database;

Logmode ------------ARCHIVELOG V$archived_log: It will show all archived logs information

Sql;>select name,dest_id,thread#,sequence#,arechived,completion fromv$archived_log;

Name Dest_id thread# /stage/-1 1 -44-66-dbf

sequence# archived completion 44 yes ly_sep-08

V$archived_dest:

Sql> select def_name,name_space,arctuver,log_sequence From v$archive_dest;

Dest_name name_space archiver log_sequence -------------------------------------------------------------------------------------------Log_archive_dest system arch 0 V$backup_redolog. V$log. V$loghistory. Q) what is the role to grant users to allow select pr ivileges on all data dictionary views? Select_catalog_role. Q)what is role to grant users to allow excute privilages for packages and And procedures in data dictionary? Excute_catolog_role. Q) role to delete records from system audit table(aud$) delete_catalog_role. Page 89 of 102

DBA NOTES Q) role to allow query access to any object in the sys schema. Select any distionary. AUTHENTICATION the Authentication which we can define users such that the database performs both identification and authentication of users is said to be database Authentication. The authentication through whiech we can define users that Authentication is performed by o/s or network service Is called external authentication. o/s level authentication: to connect to database.  create user exactly as o/s account

Sql> create user ops$ramesh is identified externally;

grant privilages to ops$rameh;  make sure that the parameter value Os_authent_prefix =ops$. It is default value We can change this value in init ora connect to sqlplus as follows $ sqlplus / Q) How can we view memory used for each user session? Sql> select username,value || ‘Bytes’ “current uga memory” from v$selssion sess, v$sesstat stat,v$statname name where sess.sid=statsid and stat.statistic#=name.statistic# and name.name=’session uga memory’;

Username ------------------Sys System Am

current uga memory. --------------------------------941824 Bytes 226720 Bytes 156256 Bytes

How can we see the curent Licessing Limits? SQL> select session_max s_max, sessions_warning s_warning, sessions_current s_warning sessions_current, sessions_heghwater s_high, users_max from v$license;

s_max s_warning 0

0

s_cyrrent

s_high users_max 3

3

0

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DBA NOTES

During NOMOUNT stage the below tables we can acces V$SGA SQL>select * from v$SGA;

Name

Value

Fixed size

1219352

Fariable size

184550632

Database Buffers

159383552

Redo Buffers

2973696

V$INSTANCE SQL> select instance_num,ber,instance_name,host_name,version, startup_time, status from v$ Instance;

I_N I_N H_N VER startup_time started -----------------------------------------------------------------------------------------1 app linux2 10.2.01.0 24-sep-08 started SQl>select archiver,Logins,shutdown_pending, Database,status,blocked, active_status form v$ Instance;

Achiver Logins Shutsown Database blocked Active -------------------------------------------------------------------------------------------Stopped allowed No active no normal V$log_history. V$fixed_table

Sql> select name from v$fixed_table where name like ‘v%’;

It displays dynamic performance tables. All the v$views can be accesible in mount stage. V$fixed_View_definition:From this table we can get same queries.

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DBA NOTES Sql> select view_definition from v$fixed_view_definition Where view_name=”v$instance”;

It displays query to get information about instance. AWK [Linux Command] This command is used to select and print a particular in output (or) a fiel. $ ps –ef|grep smon Gopal applmgr

8052 1 18947 1

0 15:12 ? 0 16:08 ?

00:00:00 ora_smo_mydb 00:00:00 ora_smo_mydb

$ ps –ef|grep smon|awk ‘{print $2}’ 8052 18947 By mentioning flag ‘F’ we can comment Awk -F “:” ‘{print $2}’ RM:$ rm –rf * It will remove all directories. $ rm -ia * It will ask for confirmation. DATE:$ date Fri sep 26 16:20:01 1st 2008 $ date +%d 26 $date +%m. 09 $date +%y. 08 We can create a with two todays date also $ mxdir ‘date +%dm%y’

particular word.

It creates a directory as 260908

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DBA NOTES Q) What is the use of ignore=y in import? While importing tables, it assumes that the table does not exit. If the table exists it skips out with error. To ignore this type of errors we use ignore=y Q) What the pre requisite to import user? User must exit in target Q) What is the pre requisite to import database? Database must exists on target  If we are using same file system on source and target, fallow below steps • create an empty DB • export source DB and import it. • • • •

 If we are using different file systems export the source DB create on empty DB create all the tablespaces in target DB which exists in source DB Import on target DB

Q)How can we migrate a table from DB to another DB?  export the table by using below command

[app@linux6 ~]$exp kittu/kittu file=a.dump log=a.log tables=abc

 copy dump file from source to target  Import the table using imp we had to make sure to which user we are importing. [kittu@linux6 ~]$ imp app/app file=a.dmp log=a.log tables=abc fromuser=kittu touser=app

Q) How can we migrate multiple tables? $ exp kittu/kittu file=a.dump log=a.log tables=a,b copy dump file from source to target $imp app/app file=a.dmp log=a.log tables=a,b fromuser=kittu touser=app

Q) How can we migrate multiple tables from different users(schemas)?

[app@linux8~]$ exp system/manager file=a.dmp tables=kittu.a, kittu.b, potti.b

Copy the dump file from source to target

[kittu@linux8 ~]$ imp system/manager file=a.dmp fromuser=kittu touser=app

It will import only kittu tables To import potti’s tables:

[kittu@linux8 ~]$imp system/manager file=a.dmp fromuser=potti Touser=app

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DBA NOTES

Q) How can we import only tables structure without data?  

[app@linux8 ~]$exp system/manager file=a.dmp tables=kittu.a rows=n log=a.log [app@linux8 ~]$imp system/manager file=a.dmp fromuser=kittu touser=app

Q) How can we export data using par file? $vi ram.par File =a.dmp table=abc $exp parfile=ram.par

Q)How can we import the table to target if the table already exists on target? [app@linux6 ~]$exp system/manager file=a.dmp tables=kittu.a log=a.log [kittu@linux6 ~]$emp system/manager file=a.dmp fromuser=kittu touser=app ignore=y

Q) How can we migrate a schema from DB to another? User must exists on the target database  export the schema’s data by using below syntax [app@linux6 ~]$exp system/manager file=a.dmp log=a.log owner=kittu

 copy the dump file from source to target and also create user in the target import the schema’s data by using below sysntax [kittu@linux6 ~]$imp system/manager file=a.dmp fromuser=kittu touser=kittu

Q)How can we migrate full database to other db? If we are using same file system, we migrate it easily. But if we are using different file systems, we need to sync the tablespaces on both sides ie., we are required to create the tablespace on target side what are there in source side. This must be done as system or sys user 1. [app@linux6 ~]$exp file=a.dmp log=a.log full=y 2. copy the dump file to target 3. create the tablespaces on target DB

[app@linux6 ~]$imp file=a.dmp log=a.log full=y ignore=y

Q) How can we export and import large database whole size is 500GB? This is possible by using filesize and file options in export  [app@linux6 ~]$exp system/manager filesize=100GB

file=a.dmp,b.dmp,c.dmp,d.dmp,e.dmp log=a.log full=y

 copy the dump file to target [app@linux6 ~]$ imp system/manager file=a.dmp, b.dmp, c.dmp, d.dmp, e.dmp log=a.log full=y ignore=y

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DBA NOTES

Q) From where we can find the tablespace block size? Select tablespace_name, block size from dba_tablespace Transport Tablespace:Usually if we are migrating a user which contains 1GB, it takes move time to export and import to reduce the time, export/import has an option transport_tablespace. By using this option we get the information about the metadata of tablespace Process: 1. Make the tablespace read only

sql>alter tablespace read only;

2. Export the tablespace metadata only. This process can be done as ‘SYSDBA’ user only. [app@linux6 ~]$ exp file=a.dmp tansport_tablespace=y tablespaces=app log=a.log

3. Copy the dump file from source to target also copy the datafile related to that tablespace from source to target. 4. If we are using same block size on bothsides no problem, otherwise we need to mention block size related parameter (db_2k_cache_size) in init file of target db and import the dump file [kittu@linux6 ~]$ imp file=a.dmp tansport_tablespace=y tablespaces=app Datafiles/oraAPP/kittu/kittudb/app.dbf ignore=y log=a.log SQL> alter tablespace ts01 offline immediate;

Usally when we put tablespace in offline mode, ckpt occurs for that tablespace. But by using the above option, the ckpt doesnot occurs for the tablespace only Ts is put in readonly mode. Q) Script for exporting tables and ftp to another server? vi expscript Export ORACLE_SID=${1} Export ORACLE_HOME= `grep -w ${1} /etc/oratab|awk -F ":" '{print $2}'` Export PATH =$PATH:$ORACLE_HOME/bin Export d=`date '+%d%m%y'` exp system/manager file=s_db_${d}.dmp Log =s_db_${d}.log tables=${2},${3} ftp –n set pagesize 10

Block Size: Block size for data block is created at the time of DB creation. We can also maintain database with datablocks having multiple block size. Actually my DB it made with 8k, DB cache retrieves the 8k blocks only. In order to get 1k,4k blocks we need to add the below parameter in init.ora file. Db_2k_cache_size=50m (2k_blocks) This statement allots 50m from 2k blocks in db_cache It is going to add additional space for 2k blocks in db cache. 4k_db_4k_cache_size 8k_db_8k_cache_size After adding the above parameters we can create the TS with different block size as below Create tablespace ts001 Datafile ‘/oraAPP/app/appdata/ts001.dbf’ size 10 blocksize 2k;

The data from db cache is flushed using LRU(least Recently used) algorithm. The advantage of having biggest blocksize is if retrives data at a time. The disadvantage of having bigger blocksize is more data is flushed into dbcache.  what is the package which validates username/passwd when we use export/import Dbms_plugts.checkuser Q) How can we bounce listener? lsnrctl reload

Q) How can we redo the activities in editor? !red (or) ctrlr

Q) How can we delete a line of selected range? :n,m d [here and m are numbers] Q) What is recursive sql? The sql’s which work on data dictionalry are said to be recursive sql Q) Public user?

Page 96 of 102

DBA NOTES It is not ment for local DBA’s, only for distributed DBA’s Sysopen is public user Q) Row chaining? Row spanned across the multiple blocks is called row chaining. It will came decreasing I/O performance. Q) Row Migration? A row completely migrating to another block, but its address is maintained in initial blocks. Both should reduce I/O Q) How can you reload stylesheets? Dbms_metadata_util.load_stylesheets Q) What we have do when import return error while importing starts? Use exclude=statistics in impdb Q) How can we Export only structure of table without Data ? By using option rows=N Q) What is the file which is used to read values of which are required for instance in P file ? i file Options used for Input:All the options in Exp are also there in imp. Some of other options are Show:Just lists file Contents (N) Ignore:It ignores the created errors (N) From user:It indicates list of owner user names To user:It indicates list of usernames Compile:It compiles Procedures, packages and functions (Y) Data files:Data files to be transported into Database Q) How can we mcrease the speed of Exp/imp ? By increasing Buffer size

Page 97 of 102

DBA NOTES

Q) How can we Export Bigger Data bases ? Using file size and file option [100 GB Data] Syn:exp System/manager file size=50G file=a.dmp,b.dmp Full=y imp System/manager file size=50G file=a.dmp,b.dmp Full=y

The order of files in Exp/imp must be same

Page 98 of 102

DBA NOTES Q)Why we need to pass ? In shell script Sql plus select to_char (startup_time,’dd_mm_yyyy startup time’ from v$instance;

hh24:mi:ss)

‘db

To find for particular session: Select to_char(logtime,’yyyy_dd_mm startup time’ from v$session;

hh24:mi:ss’)

“db

what is unix command which is used to debug a file?

 $ ser –x

To remove on week old files: Find

-name “v” –mbme +7 –exec run –rf{ } +

Or Find –name “x” –mtime –exec rm –rf{ }+

How can enable tracing for our own session We can enable tracing for our own session by setting the parameter. Sql> other session set sql_trace=true; Now find spid for the session

select sid, username form v$session where username=’RAMU’;

33

106

Select s.sid s.serial# p.sid from v$session s, v$process where s.paddr=p.addr.ad s.sid =33.

Spid=10875 Go to odump location and convert the trace file from row format to readable format by using tkprof.

Page 102 of 102