我对Oracle RMAN备份的理解

整体原则：先备份应该备份的内容，然后在此基础上进行备份的优化。为了干好这些必须掌握一些RMAN备份的基本技巧和查询等语句。

首先备份应该备份的内容：

Rman>backup database; //备份了所有的数据文件、控制文件和初始化参数文件

Rman>backup current controlfile;

Rman>backkup archivelog all;

此时已备份了所有需要的内容，接下来就是对该备份进行优化。

优化：

首先可以为以上每条命令所生成的文件定义格式：

Rman>backup database format ‘d:backupdb_%F’;

Rman>backup current controlfile format ‘d:backupctl_%F’;

Rman>backup archivelog all format ‘d:backupctl_%F’;

接下来可以把以上三条命令放入run中进行批处理执行：

Run{

#backup database

backup database format ‘d:backupdb_%F’;

#bacup ctlfile

backup current controlfile format ‘d:backupctl_%F’;

#backup arclog

backup archivelog all format ‘d:backupctl_%F’;

}

为每条命令增加通道和指定备份介质：

run{

#backup database

allocate channel ch_db device type disk format ‘d:backupdb_%F’;

backup database;

release channel ch_db;

#bacup ctlfile

allocate channel ch_ctl device type disk format ‘d:backupctl_%F’;

backup current controlfile;

release channel ch_ctl;

#backup arclog

allocate channel ch_arc device type disk format ‘d:backuparc_%F’;

backup archivelog all delete input;

release channel ch_arc;

}

紧接着可以对每个备份集进行一些细微的优化，如在备份归档日志文件时自动删除已备份的归档日志、每个备份集最多允许的文件个数、每个备份集的大小、每个备份片的大小，其中备份片的大小可能与备份介质的容量有关，比如备份到磁带机则应考虑该参数：

run{

#backup database

allocate channel ch_db device type disk maxpiecesize=100m format ‘d:backupdb_%F’;

backup filesperset 5 database;

release channel ch_db;

#bacup ctlfile

allocate channel ch_ctl device type disk maxpiecesize=100m format ‘d:backupctl_%F’;

backup current controlfile;

release channel ch_ctl;

#backup arclog

allocate channel ch_arc device type disk maxpiecesize=100m format ‘d:backuparc_%F’;

backup filesperset 20 archivelog al;

release channel ch_arc;

}

进一步的优化可以是对RMAN备份参数的一些设定，如开启控制文件的自动备份，配置备份保留策略并检查：

Rman>configure controlfile autobackup on;

Rman>configure controlfile autobackup format for device type disk to ‘d:backupautobk_ctl_%F’;

Rman>configure retention policy to recovery window of 30 days;

增加一些对过期文件生成的检查和删除命令，并将以下内容保存至db_fullbk.rman文件：

run{

#backup database

allocate channel ch_db device type disk maxpiecesize=100m format ‘d:backupdb_%F’;

backup filesperset 5 database;

release channel ch_db;

#bacup ctlfile

allocate channel ch_ctl device type disk maxpiecesize=100m format ‘d:backupctl_%F’;

backup current controlfile;

release channel ch_ctl;

#backup arclog

allocate channel ch_arc device type disk maxpiecesize=100m format ‘d:backuparc_%F’;

backup filesperset 20 archivelog al;

release channel ch_arc;

}

allocate channel for maintenance device type disk;

crosscheck backupset;

delete obsolete;

至此，用RMAN对数据库进行全备份的命令就已经准备完成。接下来将准备增量备份的命令，其实就是在全部命令的基础上增加了incremental level=1的设置，并将以下内容保存成db_incbk.rman文件：

run{

#backup database

allocate channel ch_db device type disk maxpiecesize=100m format ‘d:backupdb_%F’;

backup incremental level=1 filesperset 5 database;

release channel ch_db;

#bacup ctlfile

allocate channel ch_ctl device type disk maxpiecesize=100m format ‘d:backupctl_%F’;

backup current controlfile;

release channel ch_ctl;

#backup arclog

allocate channel ch_arc device type disk maxpiecesize=100m format ‘d:backuparc_%F’;

backup filesperset 20 archivelog al;

release channel ch_arc;

}

allocate channel for maintenance device type disk;

crosscheck backupset;

delete obsolete;

到目前为止，全备和增量备份的执行脚本都已准备完成，接下来就是利用操作系统来定时调用两个脚本：

（似乎）也可以在Oracle EM中进行备份调度的设置：

如果还要进行更好的优化，可以建立恢复目录，将RMAN的备份信息记录到恢复目录中去：

最后就是需要掌握一些维护RMAN的命令和相关的动态性能视图：[@more@]