RMAN-压缩选项(as compressed backupset)

Oracle10g允许你和BACKUP命令伴随使用AS COMPRESSED BACKUPSET字句，对备份集进行压缩。

这个压缩备份在恢复时无需解压缩，这一特性在以下条件下可能大为有益:

1.你的备份存储空间有限

2.通过网络备份而带宽有限

3.直接备份至磁带、CD，DVD介质而压缩不可用

你可以选择在备份命令里显示指定压缩选项:

BACKUP AS COMPRESSED BACKUPSET DATABASE PLUS ARCHIVELOG;

--仅对1,5文件压缩备份

BACKUP AS COMPRESSED BACKUPSET DATAFILE 1,5;

也可以配置RMAN指定压缩选项:

CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO COMPRESSED BACKUPSET;

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下边来做个测试来计较下他们吧：

非压缩备份

RMAN> backup database; 

Starting backup at 28-JUL-12

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=/oracle/oradata/orcl/system01.dbf

input datafile fno=00003 name=/oracle/oradata/orcl/sysaux01.dbf

input datafile fno=00005 name=/oracle/oradata/orcl/jietbs01.dbf

input datafile fno=00002 name=/oracle/oradata/orcl/undotbs01.dbf

input datafile fno=00004 name=/oracle/oradata/orcl/users01.dbf

channel ORA_DISK_1: starting piece 1 at 28-JUL-12

channel ORA_DISK_1: finished piece 1 at 28-JUL-12

piece handle=/home/oracle/app/product/10.2.0/db_1/flash_recovery_area/ORCL/backupset/2012_07_28/o1_mf_nnndf_TAG20120728T011430_815m3q6m_.bkp tag=TAG20120728T011430 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:01:06

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 28-JUL-12

channel ORA_DISK_1: finished piece 1 at 28-JUL-12

piece handle=/home/oracle/app/product/10.2.0/db_1/flash_recovery_area/ORCL/backupset/2012_07_28/o1_mf_ncsnf_TAG20120728T011430_815m5tgv_.bkp tag=TAG20120728T011430 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03

Finished backup at 28-JUL-12

消耗时间: 

00:01:06+00:00:03=1分08秒=68s

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压缩备份

RMAN> backup as compressed backupset database;

Starting backup at 28-JUL-12

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=/oracle/oradata/orcl/system01.dbf

input datafile fno=00003 name=/oracle/oradata/orcl/sysaux01.dbf

input datafile fno=00005 name=/oracle/oradata/orcl/jietbs01.dbf

input datafile fno=00002 name=/oracle/oradata/orcl/undotbs01.dbf

input datafile fno=00004 name=/oracle/oradata/orcl/users01.dbf

channel ORA_DISK_1: starting piece 1 at 28-JUL-12

channel ORA_DISK_1: finished piece 1 at 28-JUL-12

piece handle=/home/oracle/app/product/10.2.0/db_1/flash_recovery_area/ORCL/backupset/2012_07_28/o1_mf_nnndf_TAG20120728T012227_815mln9b_.bkp tag=TAG20120728T012227 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:01:15

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 28-JUL-12

channel ORA_DISK_1: finished piece 1 at 28-JUL-12

piece handle=/home/oracle/app/product/10.2.0/db_1/flash_recovery_area/ORCL/backupset/2012_07_28/o1_mf_ncsnf_TAG20120728T012227_815mo1kh_.bkp tag=TAG20120728T012227 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03

Finished backup at 28-JUL-12

消耗时间:00:01:15+ 

00:00:03

 

=1分18秒=78s

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非压缩备份  CPU(18.1%)

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                 

 5483 oracle    18   0  414m  72m  40m D 18.1 10.5   0:54.36 oracle     

压缩备份  CPU(84.0%)

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                             

 5483 oracle    18   0  430m  88m  48m R 84.0 27.8   0:47.09 oracle

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非压缩备份的大小(107724800+1097728=108822528)

-rw-r----- 1 oracle oinstall 107724800 Jul 28 01:34 o1_mf_nnndf_TAG20120728T013252_815n64k8_.bkp

-rw-r----- 1 oracle oinstall   1097728 Jul 28 01:34 o1_mf_ncsnf_TAG20120728T013252_815n8llv_.bkp

压缩备份的大小(599318528+7143424=606461952)

-rw-r----- 1 oracle oinstall 599318528 Jul 28 01:28 o1_mf_nnndf_TAG20120728T012730_815mw2yz_.bkp

-rw-r----- 1 oracle oinstall   7143424 Jul 28 01:28 o1_mf_ncsnf_TAG20120728T012730_815my5v5_.bkp

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下边我们来比较下他们之前的差别:

压缩时间(非压缩:压缩)   

68s:78s    大约 4：5 (1:1.14)

压缩占磁盘的空间(非压缩:压缩)  103.78125:578.367188   大约 1：5

压缩CPU使用(非压缩:压缩)  18.1%:84.0%    大约 (1:4.67)

压缩占空间少，相对来说比较消耗CPU和时间，呵呵。