As RMAN performs the tasks using the channels which work by maintaining a session within the database as any other normal user session, it's easy to track its working using the standard database views
V$PROCESS. Using these two views together, we can identify the server processes that are used by RMAN channels and use that information for performance bottleneck troubleshooting as we would do for a normal database session, for example, by enabling tracing on it.
The easiest way to find information about the System ID (SID) of the channel is to look at the RMAN prompt. For example, the following is a partial output from a backup command:
allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=55 ...