This parameter defines the number of database files stored in a save set by RMAN with an external backup library, that is,
backup_dev_type = rman_util. For more information, see backup_dev_type.Syntax:
rman_filesperset = <number>Default: 0, which means one file per save set for non-incremental backups or all files in one save set for incremental backups
See also:
RMAN Backup with an External Backup LibraryOracle documentation