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  1. #1
    Join Date
    Dec 2008
    Toronto, Canada

    Unanswered: db cfg params self tuning results and a big question

    we just finished our 18hr performance testing (DB2 v9.5.2 on AIX 6.1). We have set db cfg params for the testing (before running test batches):

    database_memory to AUTOMATIC(4171056)
    db_mem_thresh to 10
    locklist to AUTOMATIC(116272)
    maxlocks to AUTOMATIC(98)
    pckcachesz to AUTOMATIC(8192)
    sheapthres_shr to AUTOMATIC(204800)
    sortheap to AUTOMATIC(6712)
    instance_memory (dbm cfg) to AUTOMATIC(5013983)
    shepthres (dbm cfg) to 0

    Performance improvement is abt 20% - excellent (duration of the task time went down). Here is how db cfg params were changing during the test:

    database_memory - small fluctuations during testing from initial 4171056;
    db_mem_thresh = 10;
    locklist - flucktuated between 116272 and 28189;
    maxlocks - 98 all the time;
    pckcachesz - 8192 and did not change at all;
    sheapthres_shr - fluctuated between 74776 and 582666(max);
    sortheap - flucktuated between 3512 and 23306 (max);
    instance_memory (dbm cfg) - remained 5013983 all the time;
    shepthres (dbm cfg) = 0 (for this testing);

    Now the big question is - do we keep parameters AUTOMATIC or should we lock them to max or other values? This is the only database and instance on the server. Thank you
    DB2 9.5/9.7 on Unix/AIX 6.1/Linux

  2. #2
    Join Date
    Jan 2003
    Provided Answers: 5
    I would vote to leave them automatic.


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