URGENT!! Estimate rollback segments
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Thread: URGENT!! Estimate rollback segments

  1. #1
    Join Date
    Nov 2000
    Posts
    71

    Question

    Hi dba!
    Can anyone say to me if I'm rigth about the following Thread?
    The biggest table of my DB is about 300 M with an average record of 70 bytes.
    I'm re-analizing my DB structure and I'm studing riollback segments creation.
    I know that rolback segments should be at least 10% of the biggest table.
    Do you think that 4 rollback segtments of 30 M with those storage parameters (initial 256K, next 256K optimal 2M) could be enough considering that sometimes there are delete of about 150.000 records?
    150.000 x 70 bytes is about 10 M - IS THIS CORRECT?
    What do you think?
    THANX

  2. #2
    Join Date
    Aug 2000
    Location
    York - England
    Posts
    33
    Hello

    I may be wrong but Oracle recommend having 1 rollback segment for every 4 concurrent transactions within the database. I have never read anywhere regards sizing rollback segments in association with table sizes.

    If you are carrying out a large number of deletes it may be better to have a large rollback segment that is offline until you carry out the deletes, online this big rollback segment and set the transaction for this RBS and once the deletes are finished offline the RBS

    I hope this helps
    Cheers
    :p :p :p

  3. #3
    Join Date
    Nov 2000
    Posts
    71

    Unhappy

    Thanks Slaine.
    In fact I have 4 rollback segments considering the amount of concurrent tansanction but I'd like to understand if the way I used to calculate the size is correct.I can not use th SET TRANSACTION...USE ROLLBACK SEGMENT because the operations are executed by external tools and I can't manage those transactions.I can only try to configure in the best way my rollback segments.
    If You have any other idea or if you can aswer the way i used to calculate my rollback segments tell me.
    Thaks
    Bye

  4. #4
    Join Date
    May 2000
    Location
    ATLANTA, GA, USA
    Posts
    3,136
    Monitor V$ROLLSTAT DPT.

    The average size for each segment will give good idea.

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