VMS Help Sys Parameters, SCSFLOWCUSH  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies the lower limit for receive buffers at which point SCS
    starts to notify the remote SCS of new receive buffers. For each
    connection, SCS tracks the number of receive buffers available.
    SCS communicates this number to the SCS at the remote end of the
    connection. However, SCS does not need to do this for each new
    receive buffer added. Instead, SCS notifies the remote SCS of new
    receive buffers if the number of receive buffers falls as low as
    the SCSFLOWCUSH value.

    The default value is adequate on most systems. If an SCA port is
    not configured on your system, this parameter is ignored.

    SCSFLOWCUSH is a DYNAMIC parameter.