1    /APPEND

    Opens an existing file for writing and positions the record
    pointer at the end-of-file (EOF). New records are added to the
    end of the file.

    Only sequential files allow more than one user to append records
    concurrently.

    Use the /APPEND qualifier only to add records to an existing
    file. The /APPEND and the /WRITE qualifiers are mutually
    exclusive.

2    /ERROR

       /ERROR=label

    Transfers control to the location specified by the label keyword
    (in a command procedure) if the open operation results in an
    error. The error routine specified for this qualifier overrides
    any ON condition action specified. If the /ERROR qualifier is not
    specified, the current ON condition action is taken.

    If an error occurs and the target label is successfully given
    control, the global symbol $STATUS retains the code for the error
    that caused the error path to be taken.

3    /READ

       /READ (default)

    Opens the file for reading. If you open a file with /READ, other
    users are also allowed read access to the file, but no user is
    allowed write access. If you open a file with /READ/WRITE, no
    other users are allowed access while the file is open. If you
    specify the /READ qualifier without the /WRITE qualifier, you
    must specify an existing file.

4    /SHARE

       /SHARE[=option]
       /NOSHARE (Alpha/Integrity servers only)

    Opens the specified file as a shareable file to allow other users
    read or write access. If you specify the /SHARE=READ qualifier,
    other users are allowed read (R) access to the file, but not
    write (W) access. If you specify the /SHARE=WRITE or the /SHARE
    qualifier with no option, users are allowed read and write access
    to the specified file.

    To open a file with no shared access, specify /NOSHARE or use
    OPEN/READ/WRITE.

5    /WRITE

    Opens the file for writing. The following restrictions apply to
    the /WRITE qualifier:

    o  Use the /WRITE qualifier to open and create a new, sequential
       file. If the file specification on an OPEN/WRITE command does
       not include a file version number, and if a file with the
       specified file name and file type already exists, a new file
       with a version number one greater than the existing file is
       created.

    o  Use the /READ qualifier with the /WRITE qualifier to open an
       existing file. While the file is open, no other user will have
       access to it. When the file is first opened, the pointer is
       positioned to the beginning of the file. (This differs from
       OPEN/APPEND, which positions the pointer at the end of the
       file.) You cannot use OPEN/READ/WRITE to create a new file.

    o  The /WRITE and the /APPEND qualifiers are mutually exclusive.