Database Reference
In-Depth Information
The following example configures a preconfigured (auto) and instance-specific connection. RMAN will utilize
the preconfigured (auto) channels to perform the job when no channels have been allocated within the backup and
recovery operations.
RMAN> configure channel 1 device type disk connect 'sys/password@RONDB_1';
RMAN> configure channel 2 device type disk connect 'sys/password@RONDB_2';
The RONDB_1 and RONDB_2 TNS configurations used in the preceding example are defined in instances 1 and
2, respectively, and contain pointers to individual instances. Ensure that the TNS configuration does not use a service
name that is configured to multiple instances and that the load balancing option is turned off.
All RMAN backups followed after the configurations will automatically allocate two channels over instances 1
and 2, and the workload will be balanced across instances.
Runtime (One-Time) Multichannel Configuration
Similarly, multiple channels also can be defined dynamically just for the duration of backup runtime by specifying
them within the RMAN backup script, as follows:
run
{
allocate channel 1 device type disk connect='sys/password@rondb_1';
allocate channel 2 device type disk connect='sys/password@rondb_2';
...
}
run
{
allocate channel 1 device type disk connect='sys/password@RONDB_RMAN';
......
}
When a backup is initiated with multiple channels, you will see a message similar to the following:
Starting backup at 13-NOV-12
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=102 instance=RONDB_2 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=16 instance=RONDB_1 device type=DISK
In the first example, two channels are dynamically allocated on two different instances using a predefined TNS
connect string, specific to each instance, and the TNS connection does not have the load balancing option enabled.
With this approach, you can control which channel should go to which instance, rather than relying on automatic load
balancing algorithms.
Similarly, in the second example, two channels are dynamically allocated using a TNS or service connection with
load balancing options turned on. This approach banks on the load balancing algorithm and allocates channels on
instances according to a predefined formula.
Moreover, the life of the dynamic channel is strictly limited to the runtime. Once the backup operations get
completed, the channels are no longer valid.
During a database backup, if the instance on which the backup was initiated terminates unexpectedly, the
backup job won't fail; instead, the other channel from an active instance would take over the job and complete the
backup. Assuming that, a backup operation with two channels has been initiated from instance 1 and the instance has
 
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