看到eygle大师的贴子,说压缩备份的非压缩备份的更加耗时.
http://www.eygle.com/archives/2005/03/oracle10gneeoai.html
下面测试了一把.

非压缩备份集备份
RMAN> backup datafile 14;

Starting backup at 10-JUN-08
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=241 devtype=DISK
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00014 name=/u01/u02/oradata/orcl/q01_arbspace/q01_arbspace01.dbf
channel ORA_DISK_1: starting piece 1 at 10-JUN-08
channel ORA_DISK_1: finished piece 1 at 10-JUN-08
piece handle=/u01/backup/orcl106_rman/ORCL_19_1.bak tag=TAG20080610T094000 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:04:15
Finished backup at 10-JUN-08

下面是压缩备份集备份
RMAN> backup as compressed backupset datafile 14;

Starting backup at 10-JUN-08
using channel ORA_DISK_1
channel ORA_DISK_1: starting compressed full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00014 name=/u01/u02/oradata/orcl/q01_arbspace/q01_arbspace01.dbf
channel ORA_DISK_1: starting piece 1 at 10-JUN-08
channel ORA_DISK_1: finished piece 1 at 10-JUN-08
piece handle=/u01/backup/orcl106_rman/ORCL_20_1.bak tag=TAG20080610T094524 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:02:35
Finished backup at 10-JUN-08

非压缩备份耗时04:15,而压缩备份耗时02:35,为何压缩备份耗时<不压缩备份耗时?