Rollback segment
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Thread: Rollback segment

  1. #1
    Join Date
    Apr 2001
    Location
    Vadodara, India
    Posts
    249

    Rollback segment

    I have created rollback segment with following command

    CREATE ROLLBACK SEGMENT RB15 TABLESPACE RBSDATAA STORAGE (INITIAL 3M NEXT 3M OPTIMAL 70M MINEXTENTS 20);

    when i query dba_rollback_segments

    query shows me AS

    INITIAL_EXTENT 62914560
    NEXT_EXTENT null
    MIN_EXTENTS 1
    MAX_EXTENTS 32765

    Query shows different storage value.

    what is the reason?

  2. #2
    Join Date
    Nov 2006
    Location
    Sofia
    Posts
    630
    See if tablespace RBSDATAA is locally managed
    select extent_management from dba_tablespaces
    where tablespace_name='RBSDATAA'

  3. #3
    Join Date
    Apr 2001
    Location
    Vadodara, India
    Posts
    249
    Thanks for your reply.

    Yes, RBSDATAA is locally managed tablespace

  4. #4
    Join Date
    Nov 2006
    Location
    Sofia
    Posts
    630
    Well, when you use locally managed tablespace, the STORAGE clause is ignored. The extent size is either equal to the "granule" (in case if the tablespace is with uniform extent size) or is authomatically determined by Oracle (in case if extent pollicy is authomatic)
    The storage clause however does not causes any error, for backward compatibility.
    Only the initial extent and the min extents clauses are in force, meaning that at the segment creation are allocated as many extents, as specified in the min extents clause or to reach the initial extent size.
    Generally, isnce you use locally managed tablespaces, I supose you use 9i or later and I would recommend using authomatic undo management feature

    Regards

  5. #5
    Join Date
    May 2000
    Location
    ATLANTA, GA, USA
    Posts
    3,136
    Generally, isnce you use locally managed tablespaces, I supose you use 9i or later and I would recommend using authomatic undo management feature
    Not necessary. If you can manage the tablespace with UNIFORM SIZE, then do it. Lot of fine tuning opportunities is lost if you ASSM.

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