Undo Tablespace Management

In an RAC environment, each instance is assigned with its own Undo Tablespace. Only the instance assigned to the undo tablespace can write to it, however all instances can read blocks from all the undo tablespaces.

You have to assign the undo tablespace by specifying a value to the init parameter UNDO_TABLESPACE for each instance. If you do not set this parameter then each instances will use the first available undo tablespace. If the undo tablespace is not available then system rollback segment is used.

You can switch the Undo Tablespace dynamically using the following statement,

SQL> Alter system set undo_tablespace=undotbs03 sid='prod2';

The pending offline tablespace will be unavailable for all other instances until all the transactions against that tablespace is committed.

Thanks