Architecture Faq

9I ARCHITECTURE FAQ 1. What is an Oracle Server Oracle server is a database management system which consists of an oracle instance and an oracle database. 2. What is an Oracle Instance Instance is a combination of SGA and background processes. 3. What is an Oracle database Oracle database consists of database files which provides the physical storage for database information . 4. What is SGA System Global Area used to store database information that is shared by database processes. 5. What are the mandatory background processes SMON, PMON, DBWR, LGWR, CKPT. 6. What are the components of SGA Shared pool, Database buffer cache, Redo log buffer, Large pool, Java pool. 7. What does shared pool contain Shared pool contains most recently executed SQL statements Most recently used data definitions. 8. What does database buffer cache contain It contains copies of data blocks that have been retrieved from the datafiles. 9. What does redo log buffer contain Redo log buffer records all changes made to the data for recovery purpose. 10.What is the function of SMON SMON performs instance recovery by roll forwarding the committed as Well as uncommitted transactions and rollbacks the uncommitted transactions. Colease free space in datafiles. 11. What is the function of PMON PMON cleans up after failed processes by rolling back the user’s current transactions, Releases table or row locks, resources held by user processes, restarts the dead Dispatchers. 12. What is the function of DBWR DBWR writes dirty buffers (buffers which are modified but not yet written to

Datafiles.) from buffer cache to datafiles. 13. What is the function of LGWR LGWR writes the data from redo log buffer to redo log files. 14. What is the purpose of checkpoint Purpose of checkpoint is to make sure that all the buffers in the buffer cache that were Modified prior to point in time have been written to the datafiles. 15. When does DBWR writes dirty buffers from buffer cache to datafiles When a check point occurs When dirty buffers reach thresh hold When time out occurs When a tablespace is taken offline When a tablespace is taken to read only When a tablespace is kept in begin backup mode When a table is dropped or truncated When the database is shutdown. 16. When does LGWR writes to redo log files When redo log buffer is one third full When a commit occurs Before DBWR writes to datafiles Every 3 seconds When there is 1MB of redo in redo log buffer 17. What is a parameter file Parameter file defines the characteristics of the instance 18. What are the types of parameter files Pfile, spfile 19. What is the difference between pfile and spfile Pfile is a text file , spfile is a binary file Changes to entries in pfile take effect on the next startup Changes to entries in spfile are persistent across startup and shutdown 20. What is the default location of pfile $ORACLE_HOME/dbs 21. What is the use of control file?what information it contain? Control file is used to maintain the integrity of the database.It contains information Like database name, timestamp of database creation, tablespace names, location of Datafiles and redo log files, checkpoint information, current redo log sequence Number

22. What are the logical structures of the database Tablespaces, segments, extente, blocks 23. What is a tablespace Tablespace is a logical structure of the database that consists of one or more datafiles 24. What is a segment Segment is a space allocated for a specific object within a tablespace 25. What is an extent An extent is a set of contiguous oracle blocks 26. What is an oracle block Block is a smallest unit of storage for read write operations. 27. What is the default standard block size in 9i 8k 28. What are the parameters for sizing the buffer cache,shared pool,redo log buffer Db_cache_size, shared_pool_size, log_buffer 29. What is a password file Password file authenticates privileged users to start up and shut down an oracle Instance 30. What is an archived redo log file Archived redo log files are offline copies of the redo log files that are necessary for Recovery from media failures. 31. What is a session A session is a specific connection of a user to an oracle server 32. What is PGA Memory reserved for each user process connecting to an oracle database 33. What Is dedicated server Server process handles the request of a single user process in dedicated server 34. What is shared server In shared server, multiple server process handles the requests of several user Processes 35. What is server process Server process is a program which interacts directly with oracle server 36. What is user process

User process is a program which requestsinteraction with the oracle server 37. How can we control the size of SGA SGA_MAX_SIZE parameter can control the size of sga.