Re: Rollback to Undo in a RAC env.

From: Daniel W. Fink <Daniel.Fink_at_Sun.COM>
Date: Fri, 13 Aug 2004 11:00:22 -0600
Message-id: <411CF3A6.7040601@sun.com>

Interesting question. The docs don't seem to address this particular question. According to the RAC parameter section, UNDO_MANAGEMENT is not required to be identical amongst all instances. Since each instance must have their own undo segments (in AUM the undo tablespace), I would theorize that it is possible to have the instances running in separate modes. I would be concerned about 2 things (at least). First, how will the auto undo instance perform read consistency with entries from a manual rollback segment (of course, I've never tested cr in a RAC environment)? Second, what are the recovery implications?

In terms of known problems, avoid automatic undo in a high transaction volume OLTP system. The basic process of UNDO generation and application has not really changed, so you should not see performance problems. In all the testing I have done or been exposed to, performance was never an issue that could be tied to one type of undo management versus the other.

Regards,
Daniel

GUPTA, DEEPENDER wrote:

>Hi All,
>
>I am planning to covert the undo management from MANUAL to AUTO in a RAC
>environment with 2 nodes.
>
>My question is, do I need to shutdown both the instances for doing this or
>can I change this parameter for 1 instance at a time. Can oracle mount 2
>different instances with different UNDO management at a given point of time?
>
>Last time when I upgraded the compatible parameter to 9200 I tried it one by
>one first and I got the error message ORA-1105 as one instance was mounted
>with compatible parameter 817 and I was trying to mount the other one with
>compatible parameter 9200.
>
>Also pls advise if any type of performance problems has been observed with
>AUM.
>
>Regards
>
>

Please see the official ORACLE-L FAQ: http://www.orafaq.com

To unsubscribe send email to: oracle-l-request_at_freelists.org put 'unsubscribe' in the subject line.

--
Archives are at http://www.freelists.org/archives/oracle-l/
FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html
-----------------------------------------------------------------

Received on Fri Aug 13 2004 - 11:56:24 CDT