Closes a mounted disk or magnetic tape volume for further processing
  and cancels the logical name associated  with  the  device.  If  the
  volume  is  mounted  with  the /SHARE qualifier, its logical name is
  canceled but the volume remains mounted until all processes using it
  dismount it or terminate.

  DISMOUNT  checks  for open files and other conditions that prevent a
  Files-11 volume  from  dismounting.  If  such  a  condition  exists,
  DISMOUNT  displays  messages  indicating  that  the volume cannot be
  dismounted and lists the conditions that prevent  the  dismount.  By
  default,  if  such  a  condition  exists, DISMOUNT does not mark the
  volume for dismount.

  Requires the GRPNAM and SYSNAM user privileges to dismount group and
  system volumes.

  Format:

    DISMOUNT  device-name[:]

Additional information available:

ParametersCommand QualifiersExamples

 device-name[:]

  Name of the device - either a logical name or a physical name - that
  contains the volume. If a physical name is specified, the controller
  defaults to A and the unit defaults to 0.

  If  the volume currently mounted on the device is a member of a disk
  or tape volume set, all volumes in the set  are  dismounted   unless
  the /UNIT qualifier is specified.

Additional information available:

/ABORT/CLUSTER/OVERRIDE/UNIT/UNLOAD

 /ABORT

  Requires  volume  ownership or the user privilege VOLPRO to use this
  qualifier with a volume that is not mounted  with  group  or  system
  availability.

  Specifies that the volume is to be  dismounted,  regardless  of  who
  mounted  it.  The  primary  purpose  of  the  /ABORT qualifier is to
  terminate  mount  verification.  DISMOUNT/ABORT  also  cancels   any
  outstanding  I/O requests. If the volume was mounted with the /SHARE
  qualifier, the /ABORT qualifier causes the volume to  be  dismounted
  for all of the users who mounted it.

 /CLUSTER

  Dismounts  a  volume  clusterwide.  If you specify DISMOUNT/CLUSTER,
  DISMOUNT checks for open files or other conditions that will prevent
  a  Files-11  volume  on the local node from dismounting. If DISMOUNT
  does not find any open files or  other  conditions,  it  checks  for
  conditions  on all other nodes in the cluster. If DISMOUNT finds one
  of the conditions on any node or nodes, it displays an error message
  identifying  the  device  and the nodes on which the error occurred,
  followed  by  an  error  message  indicating  open  files  or  other
  conditions on the volume.

  After  DISMOUNT successfully dismounts the volume on the local node,
  it dismounts  the  volume  on  every  other  node  in  the  existing
  VAXcluster  environment. If the system is not a member of a cluster,
  the /CLUSTER qualifier has no effect.

   /OVERRIDE=CHECKS

  Marks  a  Files-11  volume for dismounting even if files are open on
  the  volume.  If  you  specify  DISMOUNT/OVERRIDE=CHECKS,   DISMOUNT
  displays messages indicating any open files or other conditions that
  prevent dismounting, immediately followed by  a  message  indicating
  that the volume has been marked for dismounting.

  A  substantial  amount  of  time can pass between the time you enter
  DISMOUNT/OVERRIDE=CHECKS and the completion of the dismount.  Always
  wait  for the dismount to complete before you remove the volume. (To
  verify that the dismount  has  completed,  enter  the  SHOW  DEVICES
  command.)  Note that the final phase of volume dismounting occurs in
  the file system, and all open files on the  volume  must  be  closed
  before  the  actual  dismount can  be done.  Note also that the file
  system  cannot  dismount  a  volume  while  any  known  file   lists
  associated with it contain entries.

 /UNIT

  Dismounts only one volume of a volume set on the  specified  device.
  By default, all volumes in a set are dismounted.

                                    NOTE

        Avoid dismounting the  root  volume  of  a  volume  set,
        because it contains the master file directory (MFD). It
        may be impossible to access files on a volume set if the
        MFD is not accessible.

 /UNLOAD (default)
 /NOUNLOAD

  Unloads the device on which the volume is mounted.  If  you  specify
  DISMOUNT/UNLOAD,  the  volume is unloaded physically. If you specify
  DISMOUNT/NOUNLOAD, the volume is not  unloaded  physically.  If  you
  specify DISMOUNT without the /UNLOAD or the /NOUNLOAD qualifier, the
  qualifier that you specified with the MOUNT command (either  /UNLOAD
  or  /NOUNLOAD)  determines  whether  or  not  the volume is unloaded
  physically.

  1.   $ MOUNT MT: PAYVOL TAPE
          .
          .
          .
       $ DISMOUNT TAPE:

  The MOUNT command mounts the tape  whose  volume  identification  is
  PAYVOL on the device MTA0:  and assigns the logical name TAPE to the
  device.  By default, the volume  is  not  shareable.   The  DISMOUNT
  command  releases  access to the volume, deallocates the device, and
  deletes the logical name TAPE.

  2.   $ DISMOUNT/NOUNLOAD  DMA2:

  The DISMOUNT command dismounts the volume; the  /NOUNLOAD  qualifier
  requests that the volume remain in a ready state.

  3.   $ MOUNT/BIND=PAYROLL  DMA1:,DMA2:  PAYROLL01,PAYROLL02
          .
          .
          .
       $ DISMOUNT/UNIT  DMA2:

  The  MOUNT  command  mounts  PAYROLL, a two-volume set. The DISMOUNT
  command will dismount only PAYROLL02, leaving PAYROLL01  accessible.
  Avoid  dismounting  the root volume (in this case, PAYROLL01) of the
  volume set, because the master file directory (MFD) for  the  volume
  set is on the root volume.