Channel Connections to Cluster Instances with RMAN

Channel connections to the instances are determined using the connect string defined by channel configurations. For example, in the following configuration, three channels are allocated using dbauser/pwd@service_name. If you configure the SQL Net service name with load balancing turned on, then the channels are allocated at a node as decided by the load balancing algorithm.

CONFIGURE DEVICE TYPE sbt PARALLELISM 3;
CONFIGURE DEFAULT DEVICE TYPE TO sbt;
CONFIGURE CHANNEL DEVICE TYPE SBT CONNECT 'dbauser/pwd@service_name'

However, if the service name used in the connect string is not for load balancing, then you can control at which instance the channels are allocated using separate connect strings for each channel configuration, as follows:

CONFIGURE DEVICE TYPE sbt PARALLELISM 3;
CONFIGURE CHANNEL 1.. CONNECT 'dbauser/pwd@mydb_1';
CONFIGURE CHANNEL 2.. CONNECT 'dbauser/pwd@mydb_2';
CONFIGURE CHANNEL 3.. CONNECT 'dbauser/pwd@mydb_3';

In the previous example, it is assumed that mydb_1, mydb_2 and mydb_3 are SQL*Net service names that connect to pre-defined nodes in your Oracle RAC environment. Alternatively, you can also use manually allocated channels to backup your database files. For example, the following command backs up the SPFILE, controlfile, data files and archived redo logs:

RUN
{
    ALLOCATE CHANNEL CH1 CONNECT 'dbauser/pwd@mydb_1';
    ALLOCATE CHANNEL CH2 CONNECT 'dbauser/pwd@mydb_2';
    ALLOCATE CHANNEL CH3 CONNECT 'dbauser/pwd@mydb_3';
    BACKUP DATABASE PLUS ARCHIVED LOG;
}

During a backup operation, if at least one channel allocated has access to the archived log, then RMAN automatically schedules the backup of the specific log on that channel. Because the control file, SPFILE, and data files are accessible by any channel, the backup operation of these files is distributed across the allocated channels.

For a local archiving scheme, there must be at least one channel allocated to all of the nodes that write to their local archived logs. For a cluster file system archiving scheme, if every node writes the archived logs in the same cluster file system, then the backup operation of the archived logs is distributed across the allocated channels.

During a backup, the instances to which the channels connect must be either all mounted or all open. For example, if the instance on node1 has the database mounted while the instances on node2 and node3 have the database open, then the backup fails.

See Also:

Oracle Database Backup and Recovery Reference for more information about the CONNECT clause of the CONFIGURE CHANNEL statement