11gR2 RAC Backup

RAC-Database Backup

RAC Database Back Through RMAN:-

Every backup plan has a goal, which is to provide a speedy recovery. In addition, depending on what your strategy is, you need to configure your RAC accordingly. RMAN needs to make a dedicated connection, unlike a typical client, through the regular ONS (Oracle Net Services), which means all it needs is one node of the cluster. Moreover, you can allocate channels at each node of your RAC by specifying a command as such:
allocate channel x1 type sbt connect sys/password@rac1;
allocate channel x2 type sbt connect sys/password@rac2;
allocate channel x3 type sbt connect sys/password@rac3;
allocate channel x4 type sbt connect sys/password@rac4;

That way you can distribute the workload across nodes without doing all of the I/O intensive job via that connected node. Again, it depends on your architectural setup and backup policy. It could very well be that you want to do it via an nth node, which has an additional 10 Gbps card connected to your SAN and this node happens to be supporting a typical DSS system, which is not under stress during the schedule job or on an OLTP environment where that particular node purely services backup. Just an example scenario, but as I mentioned, discuss it thoroughly with your system Admins and SAN admin (should you have a SAN that is) before working on your backup strategy. While some environments may respond well to a distributed RMAN activity (a typical non-24x7 environment comes to mind), a single node might be best for a heavy 24/7 OLTP environment.

Configure the RMAN default channels.

RMAN> configure device type disk parallelism 2 backup type to compressed backupset;
RMAN> configure channel 1 device type disk connect 'sys/sys@rac1';
RMAN> configure channel 2 device type disk connect 'sys/sys@rac2';
RMAN> show all;

 
Hot backup of the entire database. 

RMAN> backup database plus archivelog; 

Crosscheck the backup. 

RMAN> list backupset summary;

RMAN> allocate channel for maintenance device type disk;
 
RMAN> crosscheck backup;
RMAN> list backupset summary;