Rollback Segment Online at Instance Startup
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Thread: Rollback Segment Online at Instance Startup

  1. #1
    Join Date
    Nov 2000
    Posts
    224

    Exclamation

    What I know, Oracle at Instance startup decides No. of Rollback segments to bring online on either of the two settings

    ROLLBACK_SEGMENTS=(RBS01,...RBS0n)
    or
    transactions=40
    transactions_per_rollback_segment=8

    transactions / transactions_per_rollback_segment

    I have the parameter ROLLBACK_SEGMENTS commented out thinking the transactions / transactions_per_rollback_segment
    will bring atleast 5 RBS online.
    But this is not happening, Why?
    What are Oracle's intention on implementing this new way of automatically bringing the RBS online based on transactions / transactions_per_rollback_segment.

    Please Clarify.

  2. #2
    Join Date
    Sep 2001
    Location
    NJ, USA
    Posts
    1,287
    If u have to use :
    transactions=40
    transactions_per_rollback_segment=8

    u should have PUBLIC rollback segments in database.
    These parameters will not activate usual (NOT PUBLIC) rollback segments.

    Oracle use parameters:
    transactions
    transactions_per_rollback_segment
    for make decision "how many PUBLIC rbs have to online after startup.

    If u have only usual (NOT PUBLIC) rollback segments, then u must
    write parameter:
    ROLLBACK_SEGMENTS=(....)

    [Edited by Shestakov on 05-24-2002 at 01:58 PM]

  3. #3
    Join Date
    Nov 2000
    Posts
    224
    Any reason why Oracle adopted this strategy of bringing them online automatically without specifying then in parameter, ROLLBACK_SEGMENTS=()

  4. #4
    Join Date
    May 2002
    Location
    California, USA
    Posts
    175
    But this is not happening, Why?
    What are Oracle's intention on implementing this new way of automatically bringing the RBS online based on transactions / transactions_per_rollback_segment.
    Sharma,

    Unless you specify the RBS names in ROLLBACK_SEGMENTS parameter, HOW does Oracle knows how you named your rollback segments, or do you have any ??????

    Here is what those parameters are created for:

    TRANSACTIONS_PER_ROLLBACK_SEGMENT specifies the number of concurrent transactions you expect each rollback segment to have to handle. The minimum number of rollback segments acquired at startup is TRANSACTIONS divided by the value for this parameter.

    TRANSACTIONS specifies the maximum number of concurrent transactions. Greater values increase the size of the SGA and can increase the number of rollback segments allocated.

    and

    ROLLBACK_SEGMENTS allocates one or more rollback segments by name to this instance.

    If you specify only TRANSACTIONS and TRANSACTIONS_PER_ROLLBACK_SEGMENT , then no private RBS would be allocated and public RBS will be used if you have any. In your case you don't have any, and that is why
    But this is not happening
    Unless, you create private RBS and specify them in ROLLBACK_SEGMENTS, or create public RBS, you will not have RBS allocated.

    That might lead you to error like THIS ONE

    Hope that helps,



    clio_usa
    OCP 8, 8i, 9i - Senior Oracle DBA
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