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Thread: Rollback segments - Wraps

  1. #1
    Join Date
    Aug 2001
    Posts
    8

    Question

    Quick and probably easy question for the resident experts in the house!

    I have just reconfigured my rollback segments, but I was wondering, are wraps good or bad? and is there a way of eliminating them?

    Rich
    Rich H

  2. #2
    If you imagine your rollback segments as a ring, with the head moving around the ring. When the head has moved around once that is a wrap. A high number of wraps indicate you shoud increase the size of your rollback segments, or allocate new ones. Wraps are not a problem unless the 'head' starts overwriting 'inactive in use' data' - that is data that is not part of an active insert/update etc, but is being read by a long running query for read consistency. If this happens you will get "SNAPSHOT TOO OLD " errors in the long running SQL. If this isnt happening then your wrapping is probably ok....

    -B

  3. #3
    Join Date
    Aug 2001
    Posts
    8
    it seems to be better than the last time, now I have no WAITS or EXTENDS which I had few of before.
    Rich H

  4. #4
    Join Date
    Feb 2001
    Posts
    82
    how can i know the no. of wraps in a rbs....

  5. #5
    Join Date
    Aug 2001
    Posts
    8
    use v$rollstat, that will provide you with most of the info. use v$rollname to get the rollback segments name.
    Rich H

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