Configuring and Backing Up Oracle Databases Using RMAN - OCP: Oracle Database 12c Administrator Certified Professional - page 132

of your tapes can hold only 200GB of data, then you would want to limit the size of each
backup set piece to 200GB.
MAXSETSIZE has essentially the same purpose, to limit the overall size of one backup set.
The downside to using MAXSETSIZE is that if you end up with a data file that is larger than
MAXSETSIZE , it will never get backed up since each data file must be backed up within the
scope of one backup set.
Control-File Autobackups
When enabled, RMAN will perform automatic control-file autobackups after each backup.
Additionally, RMAN/Oracle will automatically create a backup of the control file to disk
anytime a database change occurs that impacts the control file and the database physical
structure, such as adding a tablespace or data file.
To enable control-file autobackups through RMAN, use the CONFIGURE command with
the CONTROLFILE AUTOBACKUP ON keyword, as shown here:
RMAN> configure controlfile autobackup on;
Control-file autobackups are stored in the FRA if one is configured. You can also use
the CONFIGURE command to configure RMAN to create the control-file autobackup in a
different location, as shown in this example:
configure controlfile autobackup format for device type disk to
'/oracle01/oracle/controfilebackup/%F';
In this example, notice the use of the %F format specifier. %F is required when defining
the location of the backup control file. This will ensure that the backup control filename is
unique each time the backup is created.
Backup Optimization
Sometimes things don't change, like some of our T-shirts (they are older than we are!)
and read-only data files. When this happens, you don't need to back them up if they have
already been backed up. Backup optimization provides the ability to tell RMAN that you
don't want to back up a database data file if that backup is not needed. This saves time and
effort on the part of RMAN. RMAN still follows all the rules of retention: Backup files are
expired when they are set to expire, and if the retention policy calls for two copies of a data
file, then the data file will be backed up two times. However, on the third backup of the
database, the read-only data file will not be backed up because the two identical copies are
sufficient for recovery.
To configure backup optimization, use the CONFIGURE command with the BACKUP
OPTIMIZATION ON keyword, as shown here:
RMAN> configure backup optimization on;