DB version : 11.2.0.4
OS : Linux/Unices
The physical files on the backup media are Backup pieces. A BackupSet is a logical grouping of 1 or more physical BackupPieces
By default each Backup set usually consists of only one backup piece. I could be wrong but, personally, I haven't come across a backupset which has more than 1 backup piece. So, why do we even need a logical grouping called 'Backup set' ?