DBWR (Database Writer)
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Thread: DBWR (Database Writer)

  1. #1
    Join Date
    Oct 2000
    I am running a DB Tuning Expert program. The program informs me that my DB_BLOCK_BUFFERS is below 90 %. I edited the init.ora file and increased the DB_BLOCk_BUFFERS. Now I am getting a different message. The message is " Too high ratio of average number of blocks scanned by the DBWR (database writer)-2570.0 as compared to all scans on the LRW chain. DBRW is working to hard"

    Does anyone know how to resolve the above problem.

    Thanks in advance


  2. #2
    Join Date
    Apr 2000
    Set the DB_BLOCK_BUFFERS size to be 20 - 50% the size of the SGA. Under normal circumstances this ratio should be >= 95%

  3. #3
    Join Date
    Nov 2000

    your initial problem may have been that not enough queries are using indexes instead of a setting too low for DB_BLOCK_BUFFERS. These buffers are used to store index blocks in memory so they can be reused by other processes, and thus avoiding so many trips to disk.

    you might also try turning on tracing for a few sessions (using DBMS_SYSTEM.SET_SQL_TRACE_IN_SESSION) and looking at the trace file for the explain plans.


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