Library /sys$common/syshlp/helplib.hlb  —  EXCHANGE  MOUNT
    Makes a foreign volume and the files or data it contains
    available for processing by EXCHANGE. The EXCHANGE command MOUNT
    enters the device into internal tables maintained by EXCHANGE.

    Format

      MOUNT  device-name

      MOUNT/VIRTUAL  device-name file-name

1  –  Parameters

 device-name

    Specifies the physical device name or logical name of the device
    on which the volume is to be mounted. For MOUNT/VIRTUAL, the
    device-name parameter supplies a name for the virtual device.

 file-name

    For MOUNT/VIRTUAL only, the file-name parameter gives the name of
    the file containing the image of the foreign volume.

2  –  Description

    The EXCHANGE command MOUNT enters the description of the foreign
    volume in internal tables maintained by EXCHANGE. This command is
    different from the DCL command MOUNT, which enters the device in
    tables maintained by the OpenVMS operating system.

    A virtual volume must be explicitly mounted with the
    MOUNT/VIRTUAL command.

    If an EXCHANGE command is given on an unmounted foreign volume,
    EXCHANGE attempts to execute an implied MOUNT/FOREIGN/WRITE-
    /NODATACHECK on the device. This feature enables EXCHANGE to
    operate in the single-command DCL mode.

    If a MOUNT/FOREIGN (either implied or explicit) command is given
    for a foreign device that has not been mounted on the OpenVMS
    system, EXCHANGE issues the equivalent of the DCL command
    MOUNT/FOREIGN and attempts to make the volume known to the
    operating system. Any volume mounted in this way remains mounted
    after EXCHANGE exits.

    When EXCHANGE issues the MOUNT/FOREIGN command, the system checks
    the following:

    o  That the device has not been allocated to another user

    o  That a volume is physically loaded on the specified device

    o  For magnetic tapes, the volume accessibility field of the VOL1
       label

3  –  Qualifiers

3.1    /DATA_CHECK

       /DATA_CHECK[=(READ,WRITE)]
       /NODATA_CHECK

    Determines whether EXCHANGE performs a second operation after
    every I/O operation to verify that the data was correctly
    transferred. If you specify /DATA_CHECK=WRITE, after every
    write operation EXCHANGE rereads the data that was just written
    and compares it with the original data. If you specify /DATA_
    CHECK=READ, EXCHANGE reads each block of data twice and verifies
    that both read operations received identical data.

    It is usually more efficient to use the /DATA_CHECK option on
    the DCL command MOUNT than to use the option on the EXCHANGE
    command MOUNT. If you mount a device with the DCL command
    MOUNT/FOREIGN/DATA_CHECK, OpenVMS can use features in the
    device hardware and device driver to perform the redundant I/O
    operations.

    The RX01 and RX02 diskette drives do not contain the necessary
    features for the operating system to perform data checking. If
    you use the DCL command MOUNT/DATA_CHECK with a diskette, the
    system is unable to perform data checking (no warning message
    is displayed). EXCHANGE is able to recognize, however, that a
    diskette was mounted with the data checking option; in this case,
    EXCHANGE performs the software data checking internally, even if
    you have not specified an explicit MOUNT/DATA_CHECK command.

    If you specify the /DATA_CHECK qualifier without an option, the
    default is /DATA_CHECK=WRITE.

3.2    /FOREIGN

    Indicates that the volume is not in the standard format used by
    the OpenVMS operating system; that is, a magnetic tape volume
    is not in the standard ANSI format, or a disk volume is not in
    Files-11 format. The EXCHANGE command MOUNT mounts only foreign
    volumes. The /FOREIGN qualifier is the default. You must use the
    DCL command MOUNT to mount OpenVMS volumes.

    The default protection applied to foreign volumes is RWLP (Read,
    Write, Logical I/O, Physical I/O) for the system and owner. If
    you mount a volume currently in Files-11 format with the /FOREIGN
    qualifier, you must have the user privilege to override volume
    protection (VOLPRO), or your UIC must match the UIC on the
    volume.

3.3    /MESSAGE

       /MESSAGE
       /NOMESSAGE

    Controls whether EXCHANGE displays a message indicating that the
    volume was mounted. The default is determined by the /MESSAGE
    qualifier specified with the EXCHANGE command when EXCHANGE was
    invoked.

3.4    /VIRTUAL

    Mounts a Files-11 file as a virtual device. When you specify
    /VIRTUAL, the MOUNT command requires two parameters. The first
    parameter is a device name assigned as the name of the virtual
    device. The second parameter is the name of the Files-11 file
    that is the image of a foreign volume.

3.5    /VOLUME_FORMAT

       /VOLUME_FORMAT=option

    Defines the physical format of the volume to be processed.

3.6    /WRITE

       /WRITE
       /NOWRITE

    Controls whether the volume can be written. You can specify
    /NOWRITE to protect files by providing read-only access.
    Specifying /NOWRITE is equivalent to write-locking the device.

    The default is /WRITE. If /WRITE is specified (either explicitly
    or by default) and the volume itself is write-locked, EXCHANGE
    displays a message to inform you that the volume is write-locked.

4  –  Examples

    1.EXCHANGE> MOUNT MT:
      %EXCHANGE-I-MOUNTED, MATH06 mounted on _MTA0:

      The command in this example requests that the magnetic tape
      loaded on the device MTA0 be mounted as a foreign volume. The
      tape label is displayed, since the tape has been previously
      initialized as an ANSI-labeled tape with the label MATH06.
      This tape cannot be accessed as a Files-11 tape; it should
      be reinitialized as a DOS-11 tape during the current EXCHANGE
      session.

    2.EXCHANGE> MOUNT DMA1:
      %EXCHANGE-I-WRITELOCK, volume is write-locked
      %EXCHANGE-S-MOUNTED, volume DMA1: mounted

      The command in this example mounts the foreign volume that is
      loaded in the RK07 device DMA1, making the volume available
      for subsequent EXCHANGE commands. EXCHANGE recognizes that the
      volume itself is write-locked, and displays a message.
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