1.TCPIP> DISMOUNT DNFS3:
      Makes the file system mounted on local device DNFS3:
      inaccessible to local users.
    2.TCPIP> DISMOUNT DNFS4:[USR.MNT]
      Dismounts only the specified mount point, [USR.MNT], on local
      device DNFS4:.
    3.TCPIP> DISMOUNT DNFS5: /WAIT
      Dismounts the DNFS5:[000000] mount point and waits for it to
      occur.
    4.TCPIP> DISMOUNT /ALL
      Dismounts all mount points on all devices.
    5.TCPIP> DISMOUNT /ALL /HOST="robin"
      Dismounts all mount points served by host robin.