Like virtual disks, virtual tape devices appear as files to the host system.  By default, Avanti assigns the extension .vtape to a virtual tape file.  The vtape format utilized by Avanti is fully compatible with the vtape format used in SimH.  Avanti virtual tape devices default to a DEC DLT2000 device type.

Note:Avanti puts no limit on the size of a vtape file.  Continuously appending to a tape will eventually fill the host system disk.

Avanti treats virtual tape files as follows:

•If a virtual tape files does not exist on Avanti startup, it is created.

•If a virtual tape file is removed while Avanti is running, Avanti will create a new tape file then next time the associated tape device is accessed.  See Changing Tapes  for more on this feature.

•If a virtual tape file exists on Avanti startup, it is used.

•Avanti locks access to a tape file upon the following operations:

-Tru64: Tape read/write operations commence.

-VMS: Tape INITIALIZE or MOUNT operation is executed.  If a tape is INITIALIZE'd, its underlying file will not be unlocked until a MOUNT/DISMOUNT operation is performed or VMS is shutdown.

•Avanti releases a tape file when an UNLOAD command is sent to the virtual tape drive.  The following operations issue an UNLOAD command:

-Tru64: mt unload or mt offline operation is executed.

-VMS: Tape DISMOUNT operation is executed.

•Under VMS, when a tape is initialized, the underlying tape file is reduced to a few Kbytes in size.