VMS Help V73 Features, System Management Features, New System Parameters, WBM_MSG_LOWER  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    WBM_MSG_LOWER 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. (Write bitmaps are used by the volume shadowing
    software for minicopy operations.) The others are WBM_MSG_INT
    and WBM_MSG_UPPER. 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.

    WBM_MSG_LOWER is the lower threshold for the number of messages
    sent during the test interval that initiates single-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 threshold of messages during a
    specified interval, single-message mode switches to buffered-
    message mode.

    The minimum value of WBM_MSG_LOWER is 0 messages per interval.
    The maximum value is -1, which corresponds to the maximum
    positive value that a longword can represent. The default is
    10.

    WBM_MSG_LOWER is a DYNAMIC parameter.