DVD - Deassign Virtual Disk

  DVD is the task which deassigns  a virtual disk unit from a file.   The
  unit must be dismounted for the deassignment to complete.   To deassign
  a virtual disk unit from a file, type:

  	DVD VDn:

  	VDn:	Virtual disk UNIT to deassign. Range 0-7.

  You may wish to confirm  that the virtual  disk has been deassigned  by
  checking  the  device  listing  (DEV  VD:)  to see  that  the  unit  is
  "Offline".   Also, you may check to see that the file that was formerly
  assigned to the unit is not "locked" any more.