When RMAN needs to re-synchronize from a read-consistent version of the control file, it creates a temporary snapshot control file. RMAN needs a snapshot control file only when resynchronizing with the recovery catalog or when making a backup of the current control file.
The default value for the snapshot control file is platform-specific and depends on the Oracle home. For example, the default filename on some UNIX platforms in Oracle Database 10g is $ORACLE_HOME/dbs/snapcf_@.f. Note that if you have a flash recovery area configured, the default location for the snapshot control file is not the flash recovery area.
As of Oracle 11.2 (188.8.131.52 to more precise) the snapshot control file must be on a location shared by all RAC nodes in a cluster (it must be accessible by all nodes on which instances for an RAC database can run). If you do not do so, you most likely will receive an ORA-00245 (ORA-00245: control file backup operation failed) when running an RMAN backup.
RMAN> SHOW SNAPSHOT CONTROLFILE NAME;
CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘/oracle/dbs/snapcf_test.f’; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘<shared snapshot control file>’;
CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘+RECO/TEST/CONTROLFILE/snapcf_test.f’;
You can Restore using snapshot controlfile also
restore controlfile from ‘/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_test.f’;