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[zt] 10gR2 rman对Unused Block Compression

原创 Linux操作系统 作者:tolywang 时间:2009-02-12 16:03:00 0 删除 编辑

                在10gR2中,rman最显著的一个特征就是对未分配的块进行压缩,但它必须满足一些必要的条件,在满足该条件下做了测试,效果非常理想,创建一个2g的数据文件,备份集只增加了8m,而且数据文件总的容量在2g,备份集才588m.

备份的脚本:

rman>backup full database format = 'd:test.bak';

必须满足的条件如下:


Unused Block Compression Of Datafile Backups to Backup Sets
When backing up datafiles into backup sets, RMAN does not back up the contents of data blocks that have never been allocated. (In previous releases, this behavior. was referred to as NULL compression.)
RMAN also skips other datafile blocks that do not currently contain data, if all of the following conditions apply:
■ The COMPATIBLE initialization parameter is set to 10.2
■ There are currently no guaranteed restore points defined for the database
■ The datafile is locally managed
■ The datafile is being backed up to a backup set as part of a full backup or a level 0 incremental backup
■ The backup set is being created on disk.
Skipping unused data blocks where possible enables RMAN to back up datafiles using less space, and can make I/O more efficient. 

出处:  http://xzh2000.itpub.net/post/96/64549   

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/35489/viewspace-548869/,如需转载,请注明出处,否则将追究法律责任。

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