How RMAN behave to can use a number of the allocated channel during the backup process

I have an issue on 11.2.0.4 database (2 node RAC system) on AIX.  Our system is already around 25T and our full backup size almost 3,7Tb with using compress option. Our number of datafiles are almost 1054.  We are taking our backup to disk using 16 channel. Total full backup duration is almost 4,5 hours. […]