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素颜马尾好姑娘i 2022-08-07 06:45 181阅读 0赞

在rman增量备份中，有差异增量和累积增量的概念

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       1、概念 
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      <strong>差异增量（Differential)</strong>：是备份低级别或者相同级别备份以来变化的所有数据块，顾名思议，也就是要备前期备份以来的差异数据块 
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       &nbsp;  
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       若前面的备份同时存在低级别和相同级别，则优先选择备份从 
      <strong>最近的低级别(n-1)</strong>以来变化的数据块， 
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       若没有n-1级别备份，则选择备份 
      <strong>同级别</strong>备份以来变化的数据块, 
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       若没有同级别的备份，则备份 
      <strong>更低级别以来(n-x)</strong>变化的数据 
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       若前面同时有n-1级别和相同级别，则备份 
      <strong>相同级别</strong>以来变化的数据 
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      <br> 
      <strong>累积增量(Cumulative)</strong>：是备份n-1级别（上级）或更低级别以来变化的所有数据块 
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       &nbsp;  
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       若前面的备份同时存在低级别和n-1级别，则优先选择备份从 
      <strong>n-1级别</strong>以来变化的数据块 
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       若没有n-1级别，则备 
      <strong>更低级别的(n-x)</strong> 
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       &nbsp;  
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       2、备份策略及恢复 
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       以rman多级增量备份来作为备份策略例子: 
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       增量备份都需要一个0级备份来作为基础，0级备份与全备份的区别在于0级可以用来增量恢复，而全备份则不可以。 
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       备份策略： 
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       eg:我们对一星期做如下备份策略 
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      <a href="http://hi.baidu.com/hhit2b%D5%BD%EF%BF%BD%EF%BF%BD/blog/item/:;" style="text-decoration:none; color:rgb(40,100,70)" rel="nofollow"><u><strong><span style="color:#666666; word-wrap:normal; word-break:normal; line-height:20px">案例</span></strong></u></a>。 
      <br> 星期&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;差异增量&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;累积增量 
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        星期天&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0级 
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        星期一&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级 
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        星期二&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级 
      </div> 
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        星期三&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;1级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;1级 
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        星期四&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级 
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        星期五&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级 
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        星期六&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;2级 
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        星期天&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0级&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;0级 
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        &nbsp;  
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         &nbsp;  
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         对于差异增量，周一的二级备从周日到周一变化的数据 （没有n-1级,也没有同级别） 
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         &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周二的二级备从周一到周二变化的数据 （没有n-1级,有同级别） 
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         &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周三的一级备从周日到周三变化的数据 （没有n-1级,有同级别） 
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         &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周四的二级备从周三到周四变化的数据&nbsp; &nbsp;（有n-1级) 
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         &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周五的二级备从周四到周五变化的数据&nbsp; &nbsp; （有n-1级,有同级别） 
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         &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周六的二级备从周五到周六变化的数据&nbsp; &nbsp; （有n-1级,有同级别） 
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         &nbsp;  
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         如图： 
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         &nbsp;  
        <a href="http://space.itpub.net/batch.download.php?aid=20949" style="text-decoration:none; color:rgb(40,100,70)" rel="nofollow"><img src="http://space.itpub.net/attachments/2010/03/7607759_201003091114081.jpg" alt="关于rman差异增量及累积增量的区别明白清晰版（50%原创）" title="关于rman差异增量及累积增量的区别明白清晰版（50%原创）" style="margin:0px; padding:0px; border:0px; list-style:none"></a> 
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        &nbsp;  
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       <a href="http://space.itpub.net/batch.download.php?aid=20950" style="text-decoration:none; color:rgb(40,100,70)" rel="nofollow"></a> 
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       假如周六数据库需要恢复（周五的二级备份完毕，未备份周六的），那么差异增量只需要使用星期天的0级，星期三的一级，星期四、五的二级加归档日志就可以完全恢复 
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       &nbsp;  
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      <div>
        对于累积增量，周一的二级备从周日到周一变化的数据 (没有n-1级，有更低级别） 
      </div> 
      <div>
        &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周二的二级备从周日到周二变化的数据&nbsp; (没有n-1级，有更低级别） 
      </div> 
      <div>
        &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周三的一级备从周日到周三变化的数据&nbsp; (有n-1级） 
      </div> 
      <div>
        &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周四的二级备从周三到周四变化的数据&nbsp; (有n-1级） 
      </div> 
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        &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周五的二级备从周三到周五变化的数据 (有n-1级） 
      </div> 
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        &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;周六的二级备从周三到周六变化的数据 (有n-1级） 
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        如图示： 
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       &nbsp;  
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      <a href="http://space.itpub.net/batch.download.php?aid=20950" style="text-decoration:none; color:rgb(40,100,70)" rel="nofollow"><img height="211" src="http://space.itpub.net/attachments/2010/03/7607759_201003091114082.jpg" width="525" alt="关于rman差异增量及累积增量的区别明白清晰版（50%原创）" title="关于rman差异增量及累积增量的区别明白清晰版（50%原创）" style="margin:0px; padding:0px; border:0px; list-style:none; width:588px; height:208px"></a> 
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       &nbsp;  
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       &nbsp;  
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       假如周六数据库需要恢复（周五的二级备份完毕，未备份周六的），累积增量则需要星期天的0级，周三的一级，星期五的二级加归档日志即可进行完全恢复 
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       &nbsp;  
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以上是一个星期的备份策略,如果做长期的备份策略则只需要把备份的时间延长即可得到新的备份策略，具体需要看自己备份及恢复能够接受的程度而顶，见最后的备份策略典型备份命令如下：

零级备份  
backup incremental level 0 database;  
一级差异增量  
backup incremental level 1 database;  
一级累计增量  
backup incremental level 1 cumulative database;

备份策略典型案例：

每半年做一个数据库的全备份（包括所有的数据和只读表空间）  
每一个月做一次零级备份（不包含只读表空间）  
每个星期做一次一级备份  
每天做一次二级备份

任何数据库的更改需要重新同步CATALOG目录并重新备份（如添加数据文件）或重新备份（如修改表空间为只读）  
建议备份一段时间归档日志和定期备份归档到到磁带上

全库备份脚本  
run\{  
allocate channel c1 type disk;  
allocate channel c2 type disk;  
allocate channel c3 type disk;  
backup full tag ‘dbfull’ format ‘/u01/oradata/backup/full%u\_%s\_%p’ database  
include current controlfile;  
sql ‘alter system archive log current’;  
backup filesperset 3 format ‘/u01/oradata/backup/arch%u\_%s\_%p’  
archivelog all delete input; \#备份归档可选，可以单独定期备份  
release channel c1;  
release channel c2;  
release channel c3;  
\}

零级备份脚本  
run\{  
allocate channel c1 type disk;  
allocate channel c2 type disk;  
allocate channel c3 type disk;  
backup incremental level 0 tag ‘db0’ format ‘/u01/oradata/backup/db0%u\_%s\_%p’  
database skip readonly;  
sql ‘alter system archive log current’;  
backup filesperset 3 format ‘/u01/oradata/backup/arch%u\_%s\_%p’  
archivelog all delete input; \#备份归档可选，可以单独定期备份  
release channel c1;  
release channel c2;  
release channel c3;  
\}

一级备份脚本  
run\{  
allocate channel c1 type disk;  
allocate channel c2 type disk;  
allocate channel c3 type disk;  
backup incremental level 1 tag ‘db1’ format ‘/u01/oradata/backup/db1%u\_%s\_%p’  
database skip readonly;  
sql ‘alter system archive log current’;  
backup filesperset 3 format ‘/u01/oradata/backup/arch%u\_%s\_%p’  
archivelog all delete input; \#备份归档可选，可以单独定期备份  
release channel c1;  
release channel c2;  
release channel c3;  
\}

如果按照以上备份策略，则每天的所需要备份的数据量只有一天的改变量。而做恢复时最多要恢复当月的一个零级备份+三个一级备份+6个二级备份+当天的归档文件。如果不能接受这样的恢复时间，可以减少零级备份之间的时间间隔。在每次备份后，原则上在该备份点之前的归档日志就可以删除掉了，但是为了进一步的安全以及日后需要（如使用LOGMNR查找所需信息），建议有条件的话，归档日志保存到能够接受的时间点，可以保存在磁带等廉价存取设备上。