VMS Help SET, RMS_DEFAULT, Qualifiers, /CONTENTION_POLICY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /CONTENTION_POLICY=keyword [/SYSTEM]

    Allows you to specify fairness under high contention conditions
    for write-shared files at the process or system level. Note that
    selecting this option may noticably increase locking overhead.

    This option is disabled by default.

    In a mixed cluster environment with high contention for specific
    buckets, it is possible for accesses to write-shared files on
    nodes using read-mode global bucket locking to dominate access
    to a bucket. Nodes without this support might be denied timely
    access to the bucket.

    Additionally, it is possible to observe comparable behavior on
    all OpenVMS versions when dealing with accesses to write-shared
    files without global buffers enabled. A similar fairness issue
    between lock conversions and new lock requests may be observed in
    which the new lock requests may remain ungranted for an extended
    period of time. Use the /CONTENTION_POLICY qualifier to specify
    fairness under high contention conditions.

    The following table lists valid PROCESS keywords (/SYSTEM not
    specified):

    Keyword        Description

    NEVER          Never use the higher overhead option to improve
                   fairness for any write-shared files accessed by
                   this process; minimal overhead.
    SOMETIMES      Use this option for fairer bucket access (but
                   higher overhead) to any write-shared files with
                   global buffers enabled accessed by this process.
    ALWAYS         Use this option for fairer bucket access (but
                   higher overhead) to all write-shared files
                   accessed by this process.
    SYSTEM_        Use system setting. Note that this keyword is
    DEFAULT        disallowed with /SYSTEM.
    (default)

    The following table lists valid SYSTEM keywords (/SYSTEM also
    specified):

    Keyword        Description

    NEVER          Never use the higher overhead option to improve
    (default)      fairness for any write-shared files accessed on
                   the system; minimal overhead.
    SOMETIMES      Use this option for fairer bucket access (but
                   higher overhead) to any write-shared files with
                   global buffers enabled accessed on the system.
    ALWAYS         Use this option for fairer bucket access (but
                   higher overhead) to all write-shared files
                   accessed on the system.