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Thread: Undo mechanism

  1. #1
    Join Date
    Nov 2004
    Posts
    25

    Unanswered: Undo mechanism

    Hello all,

    I know that Oracle uses undo table spaces or rollback segments as its undo mechanism. what does DB2 use as its undo mechanism?

    Krz

  2. #2
    Join Date
    Nov 2004
    Posts
    374

    undo

    in db2 there is a mechanism of pages in the buffer and the log file - this is the only area needed.
    Best Regards, Guy Przytula

  3. #3
    Join Date
    Sep 2003
    Posts
    237
    Oracle uses undo table spaces or rollback segments not just as its rollback mechanism, but also to provide support for different isolation levels; If you have a transaction, with isolation level RR, if you read a table with 5000 records, even if you choose 2 records, you lock 5000 records and may be it will be escalated to a table lock, in DB2. Oracle will use undo. For a simple rollback, log files will suffice, because each record has before and after a change INFO.
    mota

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