About NetBackup multistreaming

On the initial call, NetBackup for Oracle with Snapshot Client returns a special entry to RMAN indicating that it supports proxy copy. It also indicates to RMAN that it supports an unlimited number of files to be proxy-copied in a single proxy copy session. The number of channels that are allocated for the RMAN backup proxy command does not control the degree of parallelism for proxy backups. RMAN uses only one channel for proxy copy backups except when a specific configuration is used.

The NB_ORA_PC_STREAMS variable controls the number of proxy copy backup streams to be started. By default, the agent initiates one backup job for all files. If the RMAN send command passes NB_ORA_PC_STREAMS, NetBackup for Oracle splits the files into the number of groups that the variable specifies based on the file size. The agent attempts to create streams of equal size and determines the number of processes that run to perform the backup.