wait event for switch log file command
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  1. #1
    Join Date
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    wait event for switch log file command

    Hi All

    The above wait event appears consistantly in my statspack report.

    My log file sizes are 5Mb (samllish in size) i have two groups with two members each.They are not on raid 5.Any ideas how do we get rid of this wait event.



    regards
    Hrishy

  2. #2
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    5MB... so small, create more groups or increase in size, i would do both

  3. #3
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    Hi Pando

    Thanks for the sugestion..I was thiking of somethin more reasonable like 20 -25 Mb..I will do this and see wheather i can elimnate this wait event.

    regards
    Hrishy

  4. #4
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    I would certainly increase the number of groups.

    As for the size, remember that you normally want some log switching: it allows the archlog to be generated (e.g. for standby) and forces a checkpoint, which would speed up an instance recovery. You may also want to limit the size to ease transmission of archlogs over the network. So the question here is: how frequently do you get a log switch with a 5MB file size? (and of course: how long is the wait? is it significant?)

  5. #5
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    Hi Dapi

    The archive logs switch at a half an hour interval.I saw this through the alert logs.The wait event si significant as revealed by the statspack report.


    I dont have a standby for this instance.

    Ideally i would have prefered a logswitch every hour.

    I will try both i guess adding one more group and increasing the size of the members to 20Mb

    any other suggestions thoughts are most welcome

    regards
    Hrishy

  6. #6
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    Originally posted by hrishy
    The wait event si significant as revealed by the statspack report.
    Significant? (Remember, something has to be in the "top five waits". If your db & application are brilliantly tuned, with all data & parsed SQL in buffers, log switches & control file writes are about the only things left to wait on! ) So my question stands - how long do you wait for a switch?

  7. #7
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    Hi Dapi

    Yes i was checking the DB infact a routine performance review and this wait event showed up in the top 5 wait events along with controlm file parallel write.

    The reason for control file parallel write being in the top 5 wait event was all the control files are placed on the same disk.

    The next significant wait event was the one for log file switch thats when i started diggin in deeper.And started looking at the log file switch rates and the sizes of the logfiles.

    what do u think ?

    regards
    Hrishy

  8. #8
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    Hrishy :

    I think still u havent answered DAPI's
    So my question stands - how long do you wait for a switch?
    funky...

    "I Dont Want To Follow A Path, I would Rather Go Where There Is No Path And Leave A Trail."

    "Ego is the worst thing many have, try to overcome it & you will be the best, if not good, person on this earth"

  9. #9
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    Hi Abhay Dapi

    I dont have exact number but in the top 5 wait events .

    The wait event corresponding to log file switch and control file parallel write contribute 52% and 10% respectively.

    regards
    Hrishy

  10. #10
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    If you're switching every 30 minutes, I would question why you are waiting that much. I would carefully look at smaller timeslices in your statspack reports (maybe 5 minutes or so) to see what is really going on.
    Jeff Hunter
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    http://marist89.blogspot.com/
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