Environment：

Oracle 10.2.0.1

Redhat 5.4 64bit

Object:RMAN COMPRESSED

在对RMAN提供的compress功能进行测试时发现在备份集的压缩比例上有了5倍多的提升，速度上居然和非压缩时候相差无几。

无压缩参数：

RMAN> backup database;

Starting backup at 05-MAY-11
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=/u01/oradata/qqdb/system01.dbf
input datafile fno=00004 name=/u01/oradata/qqdb/users01.dbf
input datafile fno=00003 name=/u01/oradata/qqdb/sysaux01.dbf
input datafile fno=00006 name=/u01/oradata/qqdb/test_tran01.dbf
input datafile fno=00007 name=/u01/oradata/qqdb/test_rm01.dbf
input datafile fno=00002 name=/u01/oradata/qqdb/undotbs01.dbf
input datafile fno=00005 name=/u01/oradata/qqdb/odu_test01.dbf
channel ORA_DISK_1: starting piece 1 at 05-MAY-11
channel ORA_DISK_1: finished piece 1 at 05-MAY-11
piece handle=/u01/flash_recovery_area/QQDB/backupset/2011_05_05/o1_mf_nnndf_TAG20110505T092033_6w3yv4fn_.bkp tag=TAG20110505T092033 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:03:57
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current control file in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 05-MAY-11
channel ORA_DISK_1: finished piece 1 at 05-MAY-11
piece handle=/u01/flash_recovery_area/QQDB/backupset/2011_05_05/o1_mf_ncsnf_TAG20110505T092033_6w3z2lmo_.bkp tag=TAG20110505T092033 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:06
Finished backup at 05-MAY-11

含压缩参数：

RMAN> backup as compressed backupset database;

Starting backup at 05-MAY-11
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=00001 name=/u01/oradata/qqdb/system01.dbf
input datafile fno=00004 name=/u01/oradata/qqdb/users01.dbf
input datafile fno=00003 name=/u01/oradata/qqdb/sysaux01.dbf
input datafile fno=00006 name=/u01/oradata/qqdb/test_tran01.dbf
input datafile fno=00007 name=/u01/oradata/qqdb/test_rm01.dbf
input datafile fno=00002 name=/u01/oradata/qqdb/undotbs01.dbf
input datafile fno=00005 name=/u01/oradata/qqdb/odu_test01.dbf
channel ORA_DISK_1: starting piece 1 at 05-MAY-11
channel ORA_DISK_1: finished piece 1 at 05-MAY-11
piece handle=/u01/flash_recovery_area/QQDB/backupset/2011_05_05/o1_mf_nnndf_TAG20110505T104713_6w43xl6s_.bkp tag=TAG20110505T104713 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:03:55
channel ORA_DISK_1: starting compressed full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current control file in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 05-MAY-11
channel ORA_DISK_1: finished piece 1 at 05-MAY-11
piece handle=/u01/flash_recovery_area/QQDB/backupset/2011_05_05/o1_mf_ncsnf_TAG20110505T104713_6w4450g2_.bkp tag=TAG20110505T104713 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:04
Finished backup at 05-MAY-11

可以发现其时间分别是：

no compress:elapsed time: 00:03:57

have compress:elapsed time: 00:03:55
居然还快了

压缩比例上：

no compress:

1009M o1_mf_nnndf_TAG20110505T092033_6w3yv4fn_.bkp

7.2M o1_mf_ncsnf_TAG20110505T092033_6w3z2lmo_.bkp

have compress:

183M o1_mf_nnndf_TAG20110505T104713_6w43xl6s_.bkp

1.1M o1_mf_ncsnf_TAG20110505T104713_6w4450g2_.bkp

有了大概6、7倍的提升。