Re: RAC and undo tablespace

On Wed, 08 Mar 2006 11:06:29 -0800, wagen123 wrote:

>> Each instance can only use one undo tablespace at a time.
>> Instances cannot share undo tablespaces.

From the "OracleŽ Database Oracle Clusterware and Oracle Real Application Clusters Administration and Deployment Guide", chapter 6, I read

"All tightly coupled branches of a distributed transaction running on a RAC database must run on the same instance."

From this I conclude that a single transaction - something involving DML and terminated by a COMMIT or ROLLBACK - really only runs on a single RAC node. Therefore the rewind stuff (the undo or rollback) for a transaction really only applies to the node that managed the transaction.

If that is true, it begs the question:

• why add the overhead of separating the undo information that would be needed when putting it into the same undo tablespace? And
• why add the overhead of managing the undo tablespace file locking (by adding more interconnect traffic) to ensure several instances do not clobber each other?

Just my guess ....

-- 
Hans Forbrich                           
Canada-wide Oracle training and consulting
mailto: Fuzzy.GreyBeard_at_gmail.com   
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