se files is distributed across all the allocated channels. For backups of the archived redo log, the actions performed by RMAN depend on the type of archiving scheme used by your Oracle RAC database.
If you use a local archiving scheme, then each instance writes the archived redo log files to a local directory. When multiple channels are allocated that have access to the archived redo log, for each archived redo log file, RMAN determines which channels have access to that archived redo log file. Then, RMAN groups the archived redo log files that can be accessed by a channel and schedules a backup job using that channel.
If each node in the cluster writes the archived redo log files to Oracle ASM, a clustered file system, or other type of shared storage, then each instance has access to all the archived redo log files. In this case, the backup of the archived redo log is distributed across all the allocated channels.
Configuring Archiving for Your Oracle RAC Database
For Oracle RAC, each instance has its own thread of redo. The preferred configuration for Oracle RAC is to configure the fast recovery area using an Oracle ASM disk group that is separate from the Oracle ASM disk group used for your data files. Alternatively, you can use a cluster file system archiving scheme.
To configure archiving for your Oracle RAC database:
On the Database Home page of Enterprise Manager Database Control, while logged in as a SYSDBA user, select Availability.
The Availability subpage appears.
In the Backup/Recovery section, under the heading Setup, select Recovery Settings.
The Recovery Settings page appears.
In the Media Recovery section, select the ARCHIVELOG mode option.
In the Log Archive Filename Format field, accept the default value, or enter the desired format.
For clustered databases, the format for the archive log file name should contain the %t modifier, to indicate which redo log thread the archived redo log file belongs to. As a best practice, the format for the archive log file name should also include the %s (log sequence number) and %r (resetlogs identifier) modifiers.
If the archive log destination is the same for all instances, then in the Archive Log Destination field, change the value to the location of the archive log destination for the cluster database.
For example, you might set it to +DATA if using Oracle ASM, or to /u01/oradata/arch if you want local archiving on each node.
If you must configure a different archive log destination for any instance, then you must go to the Initialization Parameters page and modify the LOG_ARCHIVE_DEST_1 parameter that corresponds to the instance for which you want to configure the archive log destination. The Instance column should display the name of the instance, for example sales1. Change the Value field to contain the location of the archive log destination for that instance.
About Configuring Access to the Archive Log
During recovery, because the archive log file destinations are visible from the node that performs the recovery, Oracle RAC can successfully access the archived redo log files during recovery.
If you do not use shared storage or a clustered file system to store the archived redo log files for your cluster database, then you must make the archived redo log files available to the node performing the recovery.
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