>
> Hi Ari,
>
>
> Happy X'MAS and HAPPY NEW YEAR.
>
> Please guide me how to determine the size of ROLLBACK SEGMENTS after
> creation of database.
>
> How will you change the size of ROLLBACK SEGMENTS according to
> Application requirements.
>
> Send me e-mail at your earlist.
>
> Please help me . My DBA is on holiday.
>
>
> Regards
>
>
> PRASHANT SHINDGIKAR
>
The size of the rollback segments depend mainly on if you are in a
DSS environment (such as Data Warehousing) or OLTP (data entry, etc.).
If you are doing quick, short transactions, then the rollbacks should
be small (128k or so). Otherwise, it should be as large as required.
If you have a large batch update, for example, you should have large
rollback segments (10M - 200M or more).
If there is a mixed environment (short transactions along with some
larger batch processes), then have many small rollbacks and one large.
In the batch process ,you can say "ALTER SESSION USE ROLLBACK SEGMENT rblarge;"
to dedicate a specific rollback segment (until the next commit or rollback
statement).
Be sure to specify the rollback segments in the initSID.ora file so they will be
online when the database is shut down and restarted.
Also try to have at least one rollback segment for every four concurrent
transactions within the database; if there will be 100 users updating things
simultaneously, then have 25 rollback segments.
-Ari Kaplan
Independent Oracle DBA Consultant
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