Quiescing RAC Databases
To quiesce a RAC database, use the ALTER SYSTEM QUIESCE RESTRICTED statement from one instance. It is not possible to open the database from any instance while the database is in the process of being quiesced from another instance. After all the non-DBA sessions become inactive, the ALTER SYSTEM QUIESCE RESTRICTED statement executes and the database is considered to be quiesced. In RAC, this statement affects all instances.
SQL> ALTER SYSTEM QUIESCE RESTRICTED;
To issue the ALTER SYSTEM QUIESCE RESTRICTED statement in a RAC environment, you must have the Database Resource Manager feature activated, and it must have been activated since instance startup for all instances in the cluster database. It is through the Database Resource Manager that non-DBA sessions are prevented from becoming active. The following conditions apply to RAC:
- If you had issued the ALTER SYSTEM QUIESCE RESTRICTED statement, but the Oracle server has not finished processing it, then you cannot open the database.
- You cannot open the database if it is already in a quiesced state.
- The ALTER SYSTEM QUIESCE RESTRICTED and ALTER SYSTEM UNQUIESCE statements affect all instances in a RAC environment, not just the instance that issues the command.
Cold backups cannot be taken when the database is in a quiesced state because the Oracle background processes may still perform updates for internal purposes even when the database is in a quiesced state. Also, the file headers of online data files continue to appear as if they are being accessed. They do not look the same as they do when a clean shutdown is done.