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.

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    /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.

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.

5    /VOLUME_FORMAT

       /VOLUME_FORMAT=option

    Defines the physical format of the volume to be processed.

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.