A file specification for the backup file. The default file type
    is .rbf.

    If you use multiple tape drives, the backup-file-spec parameter
    must include the tape device specifications. Separate the device
    specifications with commas. For example:

    $ RMU/DUMP/BACKUP_FILE $111$MUA0:PERS_FULL.rbf,$112$MUA1: -
    _$ /LABEL=BACK01

    When multiple volume tape files are processed, Oracle RMU
    dismounts and unloads all but the last volume containing the
    file, which is the customary practice for multiple volume tape
    files. See the Oracle Rdb Guide to Database Maintenance for more
    information on using multiple tape drives.