ALTER SYSTEM SUSPEND statement halts all input and output (I/O) to datafiles (file header and file data) and control files. The suspended state lets you back up a database without I/O interference. When the database is suspended all preexisting I/O operations are allowed to complete and any new database accesses are placed in a queued state.
The suspend command is not specific to an instance. In an Oracle Real Application Clusters environment, when you issue the suspend command on one system, internal locking mechanisms propagate the halt request across instances, thereby quiescing all active instances in a given cluster. However, if someone starts a new instance another instance is being suspended, the new instance will not be suspended.
ALTER SYSTEM RESUME statement to resume normal database operations. The
RESUME commands can be issued from different instances. For example, if instances 1, 2, and 3 are running, and you issue an
ALTER SYSTEM SUSPEND statement from instance 1, then you can issue a
RESUME statement from instance 1, 2, or 3 with the same effect.
The suspend/resume feature is useful in systems that allow you to mirror a disk or file and then split the mirror, providing an alternative backup and restore solution. If you use a system that is unable to split a mirrored disk from an existing database while writes are occurring, then you can use the suspend/resume feature to facilitate the split.
The suspend/resume feature is not a suitable substitute for normal shutdown operations, because copies of a suspended database can contain uncommitted updates.
Caution:Do not use the
ALTER SYSTEM SUSPENDstatement as a substitute for placing a tablespace in hot backup mode. Precede any database suspend operation by an
ALTER TABLESPACE BEGIN BACKUPstatement.
The following statements illustrate
ALTER SYSTEM SUSPEND/RESUME usage. The
V$INSTANCE view is queried to confirm database status.
SQL> ALTER SYSTEM SUSPEND; System altered SQL> SELECT DATABASE_STATUS FROM V$INSTANCE; DATABASE_STATUS --------- SUSPENDED SQL> ALTER SYSTEM RESUME; System altered SQL> SELECT DATABASE_STATUS FROM V$INSTANCE; DATABASE_STATUS --------- ACTIVE
See Also:Oracle Database Backup and Recovery User's Guide for details about backing up a database using the database suspend/resume feature