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Thread: Rollback segments waits

  1. #11
    Join Date
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    Thanks For your help folks.
    I will not be adding just yet.

    Suresh
    Once you have eliminated all of the impossible,
    whatever remains however improbable,
    must be true.

  2. #12
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    80 in XACTS means active transactions but if there are no waits why would we have to add more RBS? Plus you said if you see 1 in XACTS you have to add more RBS (but now you changed your mind and said 80?)

  3. #13
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    Wraps ?

    One More thing.

    Checking the wraps column, I have about 20 - 25 per segment. my understaning of wraps is the amount of extents used in the rolback segments (when the segment extends from one extent to another). I would have thought that the only cost of this would be recursive sql.

    Is 20 -25 extents a 'safe' number ?

    If I were to have LMT RBS would this mean that there would be no cost of wraps ?

    Thanks

    Suresh
    Once you have eliminated all of the impossible,
    whatever remains however improbable,
    must be true.

  4. #14
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    Re: Wraps ?


    A wrap is when the transaction moves from one extent of the RBS to another.

    You cannot say if many or few wraps is a good or a bad thing. If SHRINKS is high then you may want to increase OPTIMAL.

    Create you RBSs with 20 extents and use OPTIMAL (= 20*size_of _an_extent)

  5. #15
    Join Date
    Oct 2000
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    467
    hi,
    If wraps are too high..you may also consider sizing your extents bigger.

    Cheers
    Vinit

  6. #16
    Join Date
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    Makati, Philippines
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    hi pando,
    I quote that 80 from you but I re-read your post and I was wrong.
    If you remember earlier I always mention IN ALL OF YOUR RBS and
    MOST OF THE TIME.
    In other words all of your rbs is busy most of the time with more than
    1 active transaction each rbs.

    If this happens do you think your gets/waits ratio will not be affected?
    Let's say you have 20 rbs and only 1 tablespace/datafile source in
    one disk do you think there is no I/O contention?

    I have problem with my AIX netscape browser... always delay in posting.
    : )

  7. #17
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    Originally posted by vinit
    hi,
    If wraps are too high..you may also consider sizing your extents bigger.

    Cheers
    You cannot tune or give optimal numbers for wraps!

    Say, you have large extents (5M) and very small transactions, you will probably never see a wrap, but else you may have many.


  8. #18
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    well according to you I should create one rbs per transaction

    even my RBS are always busy, if there are not waits why should I create more? Itīs like if I have a restaurant, I have 10 waiters, my restaurant is always full but my waiters dont make my customer wait why should I hire more waiters??

    I dont understand why you emphasize one active transaction per rbs all the time, a RBS holds more than one tramsaction, if I have 20 extents per RBS I can perfectly have several transactions in one single RBS without much contention

    [Edited by pando on 10-04-2001 at 09:47 AM]

  9. #19
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    Sep 2001
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    Makati, Philippines
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    Sure one rbs can handle more than one transaction.
    But what I emphasize, if this happens most of the
    time(numerous transaction one after the other)
    in all rbs, then I say your gets/waits ratio goes down
    and that you need to add another rbs.


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