Making Backups with RMAN - RMAN Recipes for Oracle Database 12c - page 216

Starting backup at 12-SEP-12
using channel ORA_DISK_1
skipping datafile 1; already backed up on 12-SEP-12
skipping datafile 2; already backed up on 12-SEP-12
skipping datafile 3; already backed up on 12-SEP-12
skipping datafile 4; already backed up on 12-SEP-12
skipping datafile 5; already backed up on 12-SEP-12
skipping datafile 6; already backed up on 12-SEP-12
skipping datafile 7; already backed up on 12-SEP-12
Finished backup at 12-SEP-12
Starting backup at 12-SEP-12
current log archived
using channel ORA_DISK_1
...
Finished backup at 12-SEP-12
Starting Control File Autobackup at 12-SEP-12
piece
Finished Control File Autobackup at 12-SEP-12
RMAN>
The previous backup command will back up all the database files and archive logs that weren't backed up during
the past 24 hours. Any database file or archive logs that were backed up during the past 24 hours won't be backed
up again. You thus avoid backing up files you already backed up. When RMAN encounters database files that it had
already backed up before the backup failed, it issues messages such as these:
RMAN-06501: skipping datafile 1; already backed up on SEP 12 2012 20:12:00
RMAN-06501: skipping datafile 2; already backed up on SEP 12 2012 20:13:35
RMAN-06501: skipping datafile 3; already backed up on SEP 12 2012 20:14:50
The backup command that produced this output used a SQL expression of type date ( sysdate-1 ). You may also
specify a date string as a literal string that matches the nls_date_format environment variable setting.
How It Works
The restartable backup feature backs up only those files that weren't backed up since a specified date and uses the last
completed backup set or image copy as the restart point for the new backup. By using the restartable backup feature after
a backup failure, you back up the parts of the database that the failed backup didn't back up. If your backup consists of
multiple backup sets and the backup fails midway, you don't have to back up the backup sets that were already backed up.
However, if your backup consists only of a single backup set, a backup failure means that the entire backup must be rerun.
All the database files are affected when you place the not backed up since clause right after the backup
command, as shown in our example. By placing the not backed up since clause after a specific backup set, you can
limit the backup to only the objects that are part of the backup set.
It's important to understand that when considering the number of backups, RMAN takes into account only those
backups made on a device identical to the device in the current backup command.