/sys$common/syshlp/helplib.hlb Sys Parameters, WBM_MSG_INT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    WBM_MSG_INT is one of three system parameters that are available
    for managing the update traffic between a master write bitmap
    and its corresponding local write bitmaps in an OpenVMS Cluster
    system. The others are WBM_MSG_UPPER and WBM_MSG_LOWER. These
    parameters set the interval at which the frequency of sending
    messages is tested and also set an upper and lower threshold that
    determine whether the messages are grouped into one SCS message
    or are sent one by one.

    In single-message mode, WBM_MSG_INT is the time interval in
    milliseconds between assessments of the most suitable write
    bitmap message mode. In single-message mode, the writes issued by
    each remote node are, by default, sent one by one in individual
    SCS messages to the node with the master write bitmap. If
    the writes sent by a remote node reach an upper threshhold
    of messages during a specified interval, single-message mode
    switches to buffered-message mode.

    In buffered-message mode, WBM_MSG_INT is the maximum time a
    message waits before it is sent. In buffered-message mode, the
    messages are collected for a specified interval and then sent
    in one SCS message. During periods of increased message traffic,
    grouping multiple messages to send in one SCS message to the
    master write bitmap is generally more efficient than sending each
    message separately.

    The minimum value of WBM_MSG_INT is 10 milliseconds. The maximum
    value is -1, which corresponds to the maximum positive value that
    a longword can represent. The default is 10 milliseconds.

    WBM_MSG_INT is a DYNAMIC parameter.