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ORACLE 11 g DBA

ORACLE 11 g DBA. ARCHITECTURE - II. 1. 2. Architecture - 2. Database Buffer Cache. This Database Buffer Cache is the portion of SGA that holds copies of data blocks read from data files. The size of the database buffer cache is set by the initialization parameter file DB_CACHE_SIZE. 1. 2.

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ORACLE 11 g DBA

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  1. ORACLE 11g DBA ARCHITECTURE - II 1 2

  2. Architecture - 2 Database Buffer Cache This Database Buffer Cache is the portion of SGA that holds copies of data blocks read from data files. The size of the database buffer cache is set by the initialization parameter file DB_CACHE_SIZE 1 2

  3. Architecture - 2 Library Cache The shared SQL areas. Private SQL areas, PL/SQL procedure and packages, Control Structures are located in Library Cache. The size of the Shared Pool is used in determining the size of the library Cache. 1 2

  4. Architecture - 2 Data Dictionary The Data Dictionary is a set of tables and views containing metadata about the database. Oracle frequently accesses the Data Dictionary. The Data Dictionary holds data as rows instead of as buffers. 1 2

  5. Architecture - 2 What are the free buffers in the database buffer cache? A. Buffers that have changed should be flushed to the disk. B. Buffers that are currently in use. C. Buffers that are being written to disk. D. Buffers that can be overwritten. Ans. D - Buffers that can be overwritten 1 2

  6. Architecture - 2 Redo Log Buffer Redo log Buffer is a circular buffer in the SGA that holds information relating to changes made in the database in the form of redo entries. The background process, LGWR, writes the redo log buffer to the active redo log or group on disk. 1 2

  7. Architecture - 2 Which background process writes dirty buffers in the database buffer cache to the datafiles? A. SMON B. PMON C. CKPT D. LGWR E. DBWn Ans. E - DBWn 1 2

  8. Architecture - 2 • If an Oracle Server Process attempts to move a buffer to the dirty list and the list is full, it signals the Database Writer (DBWn) process, which writes the dirty buffers (modified block) back to disk, placing them on free list. • When an Oracle process accesses the buffer, the buffer is moved to the most recently used (MRU) of the LRU list. As more buffers are moved to MRU end of the LRU list, dirty buffers move towards the LRU end of the LRU list. 1 2

  9. END OF CONCEPT ORACLE 11g - ARCHITECTURE – I I 1 2

  10. ORACLE 11g DBA ARCHITECTURE - III 1 3

  11. Architecture - 3 Database Writer Max Processes: 20 This process writes the dirty buffers present in the database buffer cache to datafiles. The process does multi-block writing to disk asynchronously. 1 3

  12. Architecture - 3 Log Writer Max Processes: 1 The log writer process writes data from redo log buffer to redo log files on disk. 1 3

  13. Architecture - 3 System Monitor Max Processes: 1 This process is responsible for instance recovery, if necessary at instance startup. Functions of SMON are: • Roll Backward • Roll Forward • SMON also cleans up Temporary Segments. 1 3

  14. Architecture - 3 Process Monitor Max Processes: 1 This process is responsible for performing recovery if a user process fails. Functions of PMON are: • It will rollback uncommitted transactions • Release the locks and resource. 1 3

  15. Architecture - 3 Checkpoint Process Max Processes: 1 Checkpoint process signals the synchronization of all database files with the checkpoint information. It ensures data consistency and faster database recovery in case of crash. 1 3

  16. Architecture - 3 Recoverer Max Processes: 1 Intended for Distributed Recovery. All in-doubt transactions are recovered by this process in the distributed database setup. RECO will connect to the remote database to resolve pending transactions 1 3

  17. END OF CONCEPT ORACLE 11g - ARCHITECTURE – I I I 1 3

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