使用RMAN对RAC环境的备份

在RAC环境下，如果使用共享存储设备存储归档，则备份调度和常规备份没有不同，如下数据库使用ASM存储归档日志，两个实例的归档可以被任何一个实例上调度的RMAN程序所读取：

RMAN> crosscheck archivelog all;

using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=139 instance=rac1 devtype=DISK
validation succeeded for archived log
archive log filename=+FSHDG/rac/archivelog/2010_12_26/thread_1_seq_135.313.738771313
validation succeeded for archived log
archive log filename=+FSHDG/rac/archivelog/2010_12_26/thread_1_seq_136.257.738771335
validation succeeded for archived log
archive log filename=+FSHDG/rac/archivelog/2010_12_26/thread_1_seq_137.263.738771357
validation succeeded for archived log
archive log filename=+FSHDG/rac/archivelog/2010_12_26/thread_2_seq_75.314.738771283 
validation succeeded for archived log
archive log filename=+FSHDG/rac/archivelog/2010_12_26/thread_2_seq_76.259.738771305 
validation succeeded for archived log
archive log filename=+FSHDG/rac/archivelog/2010_12_26/thread_2_seq_77.261.738771323 
validation succeeded for archived log

如果使用了闪回区，发出的备份命令会将备份集存储在闪回区中：

RMAN> BACKUP AS COMPRESSED BACKUPSET DATABASE PLUS ARCHIVELOG;


Starting backup at 26-DEC-10
current log archived
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=139 instance=rac1 devtype=DISK
channel ORA_DISK_1: starting compressed archive log backupset
channel ORA_DISK_1: specifying archive log(s) in backup set
input archive log thread=1 sequence=135 recid=204 stamp=738771313
input archive log thread=1 sequence=136 recid=206 stamp=738771335
input archive log thread=2 sequence=75 recid=205 stamp=738771283
input archive log thread=2 sequence=76 recid=207 stamp=738771304
channel ORA_DISK_1: starting piece 1 at 26-DEC-10
channel ORA_DISK_1: finished piece 1 at 26-DEC-10
piece handle=+FSHDG/rac/backupset/2010_12_26/annnf0_tag20101226t220942_0.271
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:09
Finished backup at 26-DEC-10

Starting backup at 26-DEC-10
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=00015 name=+DATADG/rac/datafile/qidian.280.737739479
channel ORA_DISK_1: starting piece 1 at 26-DEC-10
channel ORA_DISK_1: finished piece 1 at 26-DEC-10
piece handle=+FSHDG/rac/backupset/2010_12_26/nnndf0_tag20101226t220953_0.272
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
channel ORA_DISK_1: starting compressed full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=+DATADG/rac/datafile/system.259.722961061
input datafile fno=00007 name=+DATADG/rac/datafile/testtbs1.269.726592535
input datafile fno=00008 name=+DATADG/rac/datafile/trans.270.728577593
input datafile fno=00002 name=+DATADG/rac/datafile/undotbs1.260.722961083
input datafile fno=00003 name=+DATADG/rac/datafile/sysaux.261.722961087
channel ORA_DISK_1: starting piece 1 at 26-DEC-10
channel ORA_DISK_1: finished piece 1 at 26-DEC-10
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:05
Finished backup at 26-DEC-10

在RAC环境下，如果在两个节点上都会有归档日志产生，这就使得RAC环境下的备份和单实例环境有所不同（如果归档日志存储在共享存储上，则备份和常规备份的部署就没有任何区别）。

RAC环境下归档设置可以有多种方式，有的部署是每个节点具有独立的归档路径，对于这种情况，在备份时需要分配不同的通道，以用于访问不同节点的归档日志，以下是一个示例说明：

run
{
allocate channel c1 device type disk format '/backup/%T' connect sys/oracle@rac1;
allocate channel c2 device type disk format '/backup/%T' connect sys/oracle@rac2;
backup database plus archivelog delete all input;
}

另外一种方式是使用Cluster文件系统，通过Cluster文件系统，同一个卷可以在多个节点上同时激活，这样多个节点的归档日志就可以存放在同一个目录下，对于这种情况RMAN的备份方式和单实例就没有什么不同了。