RMAN Backup Optimization

From 11G R1 onwards only undo data blocks containing undo data for not yet committed --- or rolled back --- transactions are backed up. Undo data in the undo tablespace still required to satisfy the undo retention but only containing undo records for already committed transactions are not backed up anymore. Nice if you have undo tablespaces of multiple Gb !!!

If backup optimization is configured ( see below ) then
1. Data files belonging to read only tablespaces are not backed up all the time. It is not needed anymore to use the SKIP READONLY clause. ( Note that the SKIP READONLY could not be used for RMAN backups of standby databases. )
2. Data files belonging to tablespaces which were offlined normal are not backed up all the time. It is not needed anymore to use the SKIP TABLESPACE clause.
3. The archivelog sequence is not backed up all the time. This is nice if you keep a large amount of archived redo logs on disk for whatever reason ( Logminer, Streams, Data Guard )

How to configure backup optimization ?

RMAN> configure backup optimization on;

new RMAN configuration parameters:
CONFIGURE BACKUP OPTIMIZATION ON;
new RMAN configuration parameters are successfully stored

What is the RMAN output when files are skipped during backup ?

RMAN> backup as compressed backupset database;

Starting backup at 23-JUN-09
using channel ORA_DISK_1
using channel ORA_DISK_2
skipping datafile 4; already backed up 2 time(s)
channel ORA_DISK_1: starting compressed full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00002 name=C:\ORACLE\PRODUCT\11.1.0\ORADATA\PLATINUM\DATAFILE\O1_MF_SYSAUX_0MK30K1T_.DBF
input datafile file number=00003 name=C:\ORACLE\PRODUCT\11.1.0\ORADATA\PLATINUM\DATAFILE\O1_MF_UNDOTBS1_0NK30K84_.DBF
input datafile file number=00006 name=C:\ORACLE\PRODUCT\11.1.0\ORADATA\PLATINUM\DATAFILE\O1_MF_USERS_ARCHIVE_02_0PK30K9S_.DBF
input datafile file number=00009 name=C:\ORACLE\PRODUCT\11.1.0\ORADATA\PLATINUM\DATAFILE\O1_MF_PM2_4ZM8LTBW_.DBF
input datafile file number=00011 name=C:\ORACLE\PRODUCT\11.1.0\ORADATA\PLATINUM\DATAFILE\O1_MF_CATALOG_53ZL1X82_.DBF