The file specification for the backup file. The default file
    extension is .rbf. Depending on whether you are performing a
    backup operation to magnetic tape, disk, or multiple disks, the
    backup file specification should be specified as follows:

    o  If you are backing up to magnetic tape

       -  Oracle Corporation recommends that you supply a backup
          file name that is 17 or fewer characters in length. File
          names longer than 17 characters might be truncated. See
          the Usage_Notes help entry under this command for more
          information about backup file names that are longer than 17
          characters.

       -  If you use multiple tape drives, the backup-file-spec
          parameter must be provided with (and only with) the first
          tape drive name. Additional tape drive names must be
          separated from the first and subsequent tape drive names
          with commas.

       See the Oracle Rdb Guide to Database Maintenance for more
       information about using multiple tape drives.

    o  If you are backing up to multiple or single disk files

       -  It is good practice to write backup files to a device other
          than the devices where the database root, storage area, and
          snapshot files of the database are located. This way, if
          there is a problem with the database disks, you can still
          restore the database from a backup file.

       -  If you use multiple disk files, the backup-file-spec
          parameter must be provided with (and only with) the first
          disk device name. Additional disk device names must be
          separated from the first and subsequent disk device names
          with commas. You must include the Disk_File qualifier. For
          example:

          $ RMU/BACKUP/DISK_FILE MF_PERSONNEL.RDB -
          _$ DEVICE1:[DIRECTORY1]MFP.RBF,DEVICE2:[DIRECTORY2]

          As an alternative to listing the disk device names on
          the command line (which, if you use several devices, can
          exceed the line-limit length for a command line), you can
          specify an options file in place of the backup-file-spec.
          For example:

          $ RMU/BACKUP/DISK_FILE LARGE_DB "@DEVICES.OPT"

          The contents of devices.opt might appear as follows:

          DEVICE1:[DIRECTORY1]LARGE_DB.RBF
          DEVICE2:[DIRECTORY2]

          The resulting backup files created from such an options
          file would be:

          DISK1:[DIRECTORY1]LARGE_DB.RBF
          DISK2:[DIRECTORY2]LARGE_DB01.RBF

          Note that the same directory must exist on each device
          before you issue the command. Also, if you forget to
          specify the Disk_File qualifier, you receive an error
          message similar to the following:

          $ RMU/BACKUP MF_PERSONNEL DEVICE1:[DIRECTORY1]MFP.RBF, -
          _$ DEVICE2:[DIRECTORY2]
          %RMU-F-NOTBACFIL, DEVICE1:[DIRECTORY1]MFP.RBF; is not a valid
          backup file
          %RMU-F-FTL_BCK,Fatal error for BACKUP operation at 2-MAY-2001
          09:44:57.04