the name indicates the feature is for optimizing the RMAN backups. When you
turn on this backup optimization parameter, RMAN skips the backing up the files
which has been already been backed up to the same device. The main benefit out
of this is it will reduce the unwanted space usage.
is how the RMAN determines the identical files for different categories. Below mentioned
are the only applicable categories of files.
Datafile: File must be
offline-normal or read-only or closed normally; with same DBID, checkpoint SCN,
creation SCN and resetlogs SCN and time as a datafile already in the backup.
Archived Log: the file must be
with same DBID, thread, sequence number and resetlogs SCN and time.
Backup Set: The file must be
with same DBID, backupset record ID and time stamp.
default the backup optimization will be turned off. You have to use following
command to enable the same.
RMAN> CONFIGURE BACKUP OPTIMIZATION ON;
can override the optimization at any time by using FORCE option on the
BACKUP DATABASE FORCE;
BACKUP ARCHIVELOG ALL FORCE;
RMAN> backup archivelog all;
Starting backup at 06-NOV-12
current log archived
using channel ORA_DISK_1
using channel ORA_DISK_2
using channel ORA_DISK_3
using channel ORA_DISK_4
channel ORA_DISK_1: starting compressed archived log backup set
channel ORA_DISK_1: specifying archived log(s) in backup set