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Thread: Num_log_span

  1. #1
    Join Date
    Sep 2015
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    3

    Unanswered: Num_log_span

    hi,
    I would like to knwo if the MAX_LOG is set to 60 and NUM_LOG_SPAN is set to 80 which parameter does the optimizer choose to cut off
    log running transactions.
    LOGFILSIZ - 26620
    LOGPRIMARY = 50
    LOGSECODARY = 80
    log space is 100GB

    I read the defination of both paramters from DB2 manual as
    MAX_LOG : this checks for the percentage of the log space as cut off
    NUM_LOG_SPAN : this check the number of logs before cutting transaction.

  2. #2
    Join Date
    Jan 2003
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    4,292
    Provided Answers: 5
    Whichever occurs first. MAX_LOG will fire when a transaction uses 60% of the primary log space, roughly 30 files worth, but this could be in all 50 files. NUM_LOG_SPAN will fire when a transaction spans 80 files. It can consume very little space in those 80 files.

    Andy

  3. #3
    Join Date
    Sep 2015
    Posts
    3
    hi Andy
    So just to confirm when you say "MAX_LOG will fire when a transaction uses 60% of the primary log space, roughly 30 files worth, but this could be in all 50 files. "
    Does that mean a transaction will not fill up and one single log completely before moving to the next log file and then go on to consume entire 50 files.

  4. #4
    Join Date
    Jan 2003
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    4,292
    Provided Answers: 5
    No, that is not what I meant. Assuming that you have multiple connections performing work at the same time, those separate transactions will fill up the current transaction log together, then a new log file will be used. In order for the MAX_LOGS trigger to fire, a single transaction has to use 60% of the total primary space. It does not necessarily need to be 30 complete files. It could be 60% in all 50 files, or several full and some not full. The point is that 60% of the total available primary log space is consumed by a single transaction, how that is done is irrelevant.

    Andy

  5. #5
    Join Date
    Sep 2015
    Posts
    3
    hi Andy
    Thank you for your insight and explaining between the lines of the DB2 manual is very in a very clear example.

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