Re: system tablespace rollback segment is corrupted in 8i or 9i

gazzag wrote:
> fitzjarrell_at_cox.net wrote:
> > If you've somehow corrupted your SYSTEM rollback segments (and you
> > should have at least two) you have far more serious issues with your
> > database than simple recovery could correct. The SYSTEM rollback
> > segment is used primarily for SYSTEM transactions and it's not
> > generally available for public use.
>
> I think the above needs clarification. Are you saying that you should
> have two SYSTEM rollback segments? This is not true in my experience.

I'm not saying it, the Oracle documentation is stating this:

"The Rollback Segment SYSTEM
Oracle creates an initial rollback segment called SYSTEM whenever a database is created. This segment is in the SYSTEM tablespace and uses that tablespace's default storage parameters. You cannot drop the SYSTEM rollback segment. An instance always acquires the SYSTEM rollback segment in addition to any other rollback segments it needs.

With multiple rollback segments, Oracle tries to use the SYSTEM rollback segment only for special system transactions and distributes user transactions among other rollback segments. If there are too many transactions for the nonSYSTEM rollback segments, then Oracle uses the SYSTEM segment as necessary. In general, after database creation, create at least one additional rollback segment in the SYSTEM tablespace."

I've recently added an extra SYSTEM rollback segment in our test environments, to see what impact, negative or positive, it creates. I can understand the logic of doing so; a second SYSTEM rollback segment would allow an otherwise unavailable database to be mounted and opened, as the second SYSTEM rollback segment can be used, so it could prevent downtime in the event a SYSTEM rollback segment does become corrupted or unusable.

David Fitzjarrell Received on Wed Sep 06 2006 - 08:30:25 CDT