Clears a file marked as deaccess locked. Deaccess locking is
    required by and used by those few applications that maintain
    their own locking and consistency, typically without the use
    of the OpenVMS distributed lock manager, and potentially also
    without the use of RMS. When an application using deaccess
    locking does not correctly deaccess the file (often due to an
    application or system failure), the file is marked as locked, and
    is thus inaccessible until the integrity of the contents of the
    file are verified and the SET FILE/UNLOCK command is used.

    This command does not affect the state of files that are locked
    using RMS or the distributed lock manager.

    For details on file deaccess locking, see the VSI OpenVMS I/O
    User's Reference Manual, the ACP-QIO interface documentation, and
    specifically the FIB$V_DLOCK option available on the IO$_CREATE
    and IO$_ACCESS functions.

    The SET FILE/UNLOCK command can clear the cause of the following
    error message:

    %SYSTEM-W-FILELOCKED, file is deaccess locked

    However, this command cannot resolve the cause of the error
    message:

    %RMS-W-FLK, file currently locked by another user