Assigning parallel channels for RMAN backup and resotre jobs is set with the "Number of Channels" plug-in option.
You can control the degree of parallelism within a backup job by allocating the desired number of channels. Allocating multiple channels simultaneously allows a single job to read or write multiple backup sets in parallel.
The number of channels should be less than or equal to the number of drives for the backup devices specified on the Target tab. For example, if you are targeting a VTL configured with two drives, the number of channels should be 2 or less. Use the For Tablespaces/Datafiles and For Archive Logs fields to specify the number of channels.
For backup jobs, there is additional "Channel Rate" plug-in option.
Use these settings to specify a job-specific RATE for the channels that are used during backups. (RATE is part of the ALLOCATE CHANNEL command.) While defining this RATE does not determine the actual RATE used, it does establish the maximum level for transfers, which prevents RMAN from consuming excessive bandwidth and subsequently degrading performance.
Use the For Tablespaces/Datafiles and For Archive Logs fields, and their associated unit settings, to specify the upper-limits. By default, the unit field is blank, which represents bytes. You can also select K (kilobytes), M (megabytes), or G (gigabytes).
You can also control the degree of parallelism within a restore job by allocating the desired number of channels. Allocating multiple channels simultaneously allows a single restore job to restore multiple backup sets in parallel. Like backups, the number of channels should be less than or equal to the number of channels that was specified for the backup job.
