FORCE
Causes RMAN to ignore backup optimization. In other words, even if CONFIGURE BACKUP OPTIMIZATION is set to ON, RMAN backs up all specified files.
Note: You can also specify this option in the backupSpecOperand clause.
加上FORCE选项，则RMAN忽略调CONFIGURE里的优化功能选项．
比如：你配置了RMAN优化功能为ON，之前对只读表空间作了备份，这时，再备份全库，不加FORCE.
则RMAN不会备份只读表空间，因为之前已经备份过，加上FORCE，则RMAN忽略掉优化功能，
作全库备份．
RMAN> show all;
RMAN configuration parameters are:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION ON;
SQL> alter tablespace tools read only;
Tablespace altered.
RMAN> backup tablespace tools;
Starting backup at 21-DEC-07
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00004 name=D:ORACLEORADATAPAULTOOLS01.DBF
channel ORA_DISK_1: starting piece 1 at 21-DEC-07
channel ORA_DISK_1: finished piece 1 at 21-DEC-07
piece handle=D:BACKUP3IJ454LF_1_1 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 21-DEC-07
Starting Control File and SPFILE Autobackup at 21-DEC-07
piece handle=D:BACKUPC-1605165889-20071221-03 comment=NONE
Finished Control File and SPFILE Autobackup at 21-DEC-07
RMAN> backup database;
Starting backup at 21-DEC-07
using channel ORA_DISK_1
skipping datafile 4; already backed up 3 time(s)
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=D:ORACLEORADATAPAULSYSTEM01.DBF
input datafile fno=00002 name=D:ORACLEORADATAPAULUNDOTBS01.DBF
input datafile fno=00003 name=D:ORACLEORADATAPAULINDX01.DBF
input datafile fno=00005 name=D:ORACLEORADATAPAULUSERS01.DBF
channel ORA_DISK_1: starting piece 1 at 21-DEC-07
channel ORA_DISK_1: finished piece 1 at 21-DEC-07
piece handle=D:BACKUP3KJ454M1_1_1 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:45
Finished backup at 21-DEC-07
Starting Control File and SPFILE Autobackup at 21-DEC-07
piece handle=D:BACKUPC-1605165889-20071221-04 comment=NONE
Finished Control File and SPFILE Autobackup at 21-DEC-07
RMAN> backup database force;
Starting backup at 21-DEC-07
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=D:ORACLEORADATAPAULSYSTEM01.DBF
input datafile fno=00002 name=D:ORACLEORADATAPAULUNDOTBS01.DBF
input datafile fno=00003 name=D:ORACLEORADATAPAULINDX01.DBF
input datafile fno=00005 name=D:ORACLEORADATAPAULUSERS01.DBF
input datafile fno=00004 name=D:ORACLEORADATAPAULTOOLS01.DBF
channel ORA_DISK_1: starting piece 1 at 21-DEC-07
channel ORA_DISK_1: finished piece 1 at 21-DEC-07
piece handle=D:BACKUP3MJ454NL_1_1 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:55
Finished backup at 21-DEC-07
Starting Control File and SPFILE Autobackup at 21-DEC-07
piece handle=D:BACKUPC-1605165889-20071221-05 comment=NONE
Finished Control File and SPFILE Autobackup at 21-DEC-07
RMAN>