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Thread: redo log average write time

  1. #1
    Join Date
    Dec 1999
    Tel-Aviv, Israel
    hey all!
    does anybody knows how can I calculate the average redo log
    write time?

    10x in advance.

  2. #2
    Join Date
    Aug 2001
    Look at stats on the database
    (need timed_statistics = TRUE for meaningful stats)

    A raw figure will be

    redo write time / redo writes = avg. redo write time
    This will be in writes/ 10s of millisec

    The quickest log switch interval is something different

    there is a script on called
    log_switch_interval.sql to determine this.

    I suppose some extrapolation could be used to determine the average log switch interval

    i.e redo size / redo write time = avg redo write speed
    in bytes/10s of millisec

    Then the average time will be the

    redo log size / avg redo write speed

    Have Fun
    Performance... Push the envelope!

  3. #3
    Join Date
    Feb 2001
    Paris, France
    you can know that from v$log_history, doing something like :

    select (a.first_time - b.first_time) * 3600 * 24
    from v$log_history a, v$log_history b
    where b.sequence#=a.sequence# - 1;

    this will give you time in seconds for each redo logs. from there you can get min/max/avg times.

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