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  1. #1
    Join Date
    Aug 2008
    Location
    Toronto, Canada
    Posts
    2,367

    Unanswered: bufferpool hit ratio decreased

    Let's say the bufferpool hit ratio went down for index and/or data tablespaces.


    Additional info:

    - OLTP environment
    - No configuration changes (ie. no change to tablespaces/bufferpools assignment, bp size, config parameters...)
    - STMM is OFF
    - No SQL / workload change
    - Database has been active for some time
    - No snapshot info is available before / after bp hit ratio change


    What I think happened is db2 started fetching more data due to data change / runstats execution (should invalidate cached access plan) / access plan change. So, it started doing more async vs sync I/O / rows read vs. rows selected.


    Does this sound right? Can you think of anything else?
    Last edited by db2girl; 11-12-10 at 00:07.

  2. #2
    Join Date
    Jan 2010
    Posts
    335
    Hi Bella,

    if you really can exclude the SQL / workload changes, then the most likely reason is a access plan change. This could be due to data growth or index fragmentation.

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