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Thread: Sizing log buffer

  1. #1
    Join Date
    Nov 2000
    Posts
    79
    Hi All

    What are the different ways to size log buffer ?? I am trying to tune the size of log buffer in an OLTP instance with large queris and DML's involving LOB's.


    Thanks,


  2. #2
    Join Date
    Apr 2000
    Location
    Baltimore, MD
    Posts
    759
    I think one way to get an idea about it's size is to run the utlbstat.sql/utlestat.sql during the time when large queries are being executed. Then check out the report for any Log Buffer waits and then size it accordingly.

  3. #3
    Join Date
    Nov 2000
    Posts
    79
    Thanks Halo for your suggestion.
    Just a real quick question.

    Is there a some kind of thumb rule to figure out the size of log buffer before i move on the utlbstat/utlestat ?.



    Thanks a lot.

  4. #4
    Join Date
    Jun 2000
    Location
    Madrid, Spain
    Posts
    7,447
    I dont think there is a rule but there is no need to set it very large since lgwr writes

    every 3 seconds
    every commit
    when log buffer is 1/3 full
    when log buffer is 1MB full

    This means that even you set it very big you will just waste RAM.

    I would prbably start with 512K log buffer

  5. #5
    Join Date
    Nov 2000
    Posts
    79
    Thanks Halo and Pando, Your information is really helpful.
    I would do the same.


    Thanks

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