Why we need two different Undo tablespaces for two different instances in RAC environment . What are the internals behind it ? . Any explanation regarding the concept will be great for me. What will be the scenario if we have same undo tablespace for both the instances ?
Thanks in advance .
just architecture like redo logs. I think it's a good idea to separate components (redo,undo) related to transactions.
Instances do not share undo tablespaces to reduce CONTENTION and complexity of oracle software.aslo using separate undo increase the availability of the undo datafiles.
Note: all instances can always read all undo blocks for consistent-read purposes. Also, any instance can update any undo tablespace during transaction recovery,
as long as that undo tablespace is not currently used by another instance for undo generation or transaction recovery.