Undo Tablespace
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Thread: Undo Tablespace

  1. #1
    Join Date
    Oct 2002
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    Undo Tablespace

    Hello,

    What does this dynamic extent transfer mean?

    As of Oracle8i a transaction can span multiple extents in a rollback segment but cannot span multiple segments right?

    Did this behaviour change in oracle9i?


    Thanks in advance.

  2. #2
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    yes, i believe that in 9i a transaction can employ more than one rbs
    I'm stmontgo and I approve of this message

  3. #3
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    In 9i Transaction can not span over multilple Rollback segments.
    Dilip Patel
    OCP 8i

    Catch me online at Yahoo: ddpatel256

  4. #4
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    Originally posted by Dilippatel
    In 9i Transaction can not span over multilple Rollback segments.
    Not true.

    When the first DML operation in a transaction is executed, an undo segment is chosen. The AUM transaction-bind algorithm first attempts to bind one transaction per undo segment. If such a segment cannot be found, the system will attempt to online another undo segment in the current undo tablespace. If none is available, a new undo segment is created and brought online. If none of the above steps succeed, the 8i approach is used, i.e., find the least used undo segment.

    The AUM mode supports dynamic transfer of undo space between undo segments. If an executing transaction needs more undo space, space is reused either from the current undo segment or through an extension. If none of these steps results in enough free space for the transaction, free undo space is STOLEN from other undo segments.

    Thus you will see ORA-30036 only of the undo tablespace is totally out of space.
    Oracle Certified Master
    Oracle Certified Professional 6i,8i,9i,10g,11g,12c
    email: ocp_9i@yahoo.com

  5. #5
    Join Date
    Oct 2002
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    Hello,

    What does this dynamic extent transfer mean?

    Thanks in advance.

  6. #6
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    Originally posted by oramad
    Hello,

    What does this dynamic extent transfer mean?

    Thanks in advance.
    Read the text above and you will find out!
    Oracle Certified Master
    Oracle Certified Professional 6i,8i,9i,10g,11g,12c
    email: ocp_9i@yahoo.com

  7. #7
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    Originally posted by julian
    Not true.

    When the first DML operation in a transaction is executed, an undo segment is chosen. The AUM transaction-bind algorithm first attempts to bind one transaction per undo segment. If such a segment cannot be found, the system will attempt to online another undo segment in the current undo tablespace. If none is available, a new undo segment is created and brought online. If none of the above steps succeed, the 8i approach is used, i.e., find the least used undo segment.

    The AUM mode supports dynamic transfer of undo space between undo segments. If an executing transaction needs more undo space, space is reused either from the current undo segment or through an extension. If none of these steps results in enough free space for the transaction, free undo space is STOLEN from other undo segments.

    Thus you will see ORA-30036 only of the undo tablespace is totally out of space.
    But Dilippatel's statement still holds ("In 9i Transaction can not span over multilple Rollback segments.")! This hasn't change, in any release so far the transaction is bound to one rollback segment and one rollback segment only. What has change in 9i is how undo segment can be dinamicaly extended by using unused space from some other undo segment. However the basic rule "Transaction can not span over multiple undo segments" does still apply.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

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