Extremely High Buffer Busy Waits. Please Help !!!
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Thread: Extremely High Buffer Busy Waits. Please Help !!!

  1. #1
    Join Date
    Sep 2000
    Posts
    362
    Hi,
    I ran the following the following results after running the query on v$waitstat and v$system_event tables.

    I know something is wrong but do not know the approach to fix this.

    I tried a few books also but none of them explain clearly how to fix the buffer busy waits problems clearly enough.

    Please Help.

    Thanks
    Anurag

    select * from v$waitstat where class ='data block';

    CLASS COUNT TIME
    ------------------ --------- ---------
    data block 3962775 0

    select substr(event,1,25)"Event",TOTAL_WAITS, TOTAL_TIMEOUTS,TIME_WAITED ,
    2 AVERAGE_WAIT from v$system_event where event='buffer busy waits';

    Event TOTAL_WAITS TOTAL_TIMEOUTS TIME_WAITED AVERAGE_WAIT
    ------------------------- ----------- -------------- ----------- ------------
    buffer busy waits 3962830 73 0 0



  2. #2
    Join Date
    Apr 2000
    Location
    Edison, NJ
    Posts
    759
    Temp solution:Bounce the db, run query again.

  3. #3
    Join Date
    Feb 2001
    Posts
    389
    1) Does it come during any particular query or is for whole database since startup.

    2) Either case , query v$latch , do u see any waits on
    cache hash chains.

    3) If yes , query v$filestat, find out which of the file is haveing max i/o.

    4) Query v$latch_children and find out which cache hash chain is having max of misses .

    5) Find out from the addr of this latch and match it to x$bh hladdr and find out the block which is on this latch.

    6) Find out to which object this block belongs from dba_Segment and

    a) Either tune that query or increase the freelists of that object or find out if pctfree and pctused is tuned for that(those) objects.

    Take Care
    GP

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