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Thread: wraps

  1. #1
    Join Date
    Jan 2000
    san jose
    anybody can tell me when does wrap means and when did it happen (v$rollstat) ?

  2. #2
    Join Date
    Feb 2001
    See wraps happen when Rollback segment writes from one extent to the next available extent.Here the word (AVAILABLE EXTENT) is important as rollback segment will not allocate a new extent but it will write to the next existing extent.
    When the next existing extent is being used by another transaction ,then RBS will allocate a new extent which is called a EXTEND.
    Wrapping is more beneficial and advantageous since Oracle doesnot have to allocate a new extent.RBS will use the next extent if it is free.

    e.g Ur Rollback segment is of following parameters
    initial 1M
    next 1M
    minextents 5
    maxextents 10

    Transacation A is started and will use the extent no 1.The transaction is still running so it will go to the next extent i.e No2 ,if it is free.If it is free then it is called a wrap.
    If it is not free and is used by some other transaction then RBS will allocate another extent and it calls it as extend.

    In case of any help please be free to ask me at rohitsn@altavista.com

    Rohit Nirkhe,Oracle DBA,OCP 8i

  3. #3
    Join Date
    Jun 2001
    does that means if we notify lot of wraps, we don't really care.
    but if we notice some extends, we need to figure out if rollback segment is too small.

    am i right?
    guru is on the way!!!!

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