It seems that the two instance of RAC can run in different modes. Though we should not do that and run both the instance in the same mode. I tried this in my test environment and switched the rollback to undo in 1 instance and restarted it, while the other instance was running using rollback segments. After few minutes I switched the rollback segments to undo segments in the second instance and it worked well. Conclusion is that we can switch from UNDO to ROLLBACK in a RAC env one by one and we don't need to shutdown both the instance at the same time. But the questions of Daniel are still unanswered. 1. How will the auto undo instance perform read consistency with entries from a manual rollback segment? 2. What are the recovery implications? Regards -----Original Message----- From: Daniel W. Fink [mailto:Daniel.Fink@xxxxxxx] Sent: Friday, August 20, 2004 7:54 AM To: oracle-l@xxxxxxxxxxxxx Subject: Re: Rollback to Undo in a RAC env. Well, there it is plain as day! You can't mix AUM and MUM in an instance...even though the undo_management parameters don't have to be identical ;) I understand the that undo_retention and undo_suppress_errors don't have to be the same and undo_tablespace *must* be different, so why not indicate this in the parameter section? I guess I needed to RTWholeFM. Thanks for coming across this. This is why the list is great. I don't know anyone who reads the whole manual and can remember every word. By combining our eyes and brains, we'll have read it all as a group. Daniel Senthil Ramanujam wrote: >Dan, > >I came across this document when i was searching for RAC admin stuff.. I >think this talks about maintaining same undo/rbs segment across all RAC >instances. > >http://download-west.oracle.com/docs/cd/B10501_01/rac.920/a96596/mangstor.h tm#21233 > >Note: >** > >You cannot simultaneously use automatic undo management and manual undo >management mode. In other words, all instances within Real Application >Cluster environments must operate in the same undo mode > >thanks. > >senthil > > ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html ----------------------------------------------------------------- ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------