RMAN snapshot control file

RMAN requires a consistent view of the control file under two circumstances:

• When resynchronizing with the recovery catalog
• When making a backup of the control file

To achieve these two goals, RMAN creates a temporary backup copy of the control file
called the snapshot control file, which enables RMAN to resynchronize with the recovery catalog
or back up the control file, using a read-consistent version of the control file. The default
location and name of the snapshot control file is operating system dependent. On Windows
XP, the default location is ORACLE_HOME/database, and the default name of the snapshot
control file is of the form SNCF<database name>.ORA. On Unix the default directory


Note :

Oracle allows only one RMAN session to access the snapshot control file at a time. This ensures that multiple RMAN sessions do not concurrently write and read from the snapshot control file.



CHANNEL ALLOCATION IN RMAN:

By default, RMAN comes with a single disk channel preconfigured, starting with the Oracle9i
release of the database. So, if you’re backing up to a disk, you don’t have to manually allocate
a channel. However, if you’re backing up to tape, you must either configure an automatic
channel for the tape device or manually allocate a tape (sbt) channel as part of the backup
commands you issue.

run {
allocate channel c1 device type sbt;
backup database;

}