Backup ID (BID) 

The Backint for SAP DB implementation generates a backup ID when a file or pipe is backed up, and writes this ID to the output file. This ID is then used by the functions restore, inquire, and delete.

A backup ID is not necessarily unique since it can be assigned both to the backup of a single file or pipe and to the backups of multiple files and/or pipes. However, any backup of a file is identified by a unique combination of user ID, backup ID, and file name or pipe name.