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

    PAMAXPORT specifies the maximum port number to be polled on each
    CI and DSSI. The CI and DSSI port drivers poll to discover newly
    initialized ports or the absence/failure of previously responding
    remote ports.

    A system does not detect the existence of ports whose port
    numbers are higher than this parameter's value. Thus, set this
    parameter to a value that is equal to or greater than the highest
    port number being used on any CI or DSSI connected to the system.

    You can decrease this parameter to reduce polling activity if
    the hardware configuration has fewer than 16 ports. For example,
    if the CI or DSSI with the largest configuration has a total
    of 5 ports assigned to port numbers 0 through 4, you could set
    PAMAXPORT to 4.

    If CI or DSSI devices are not configured on your system, this
    parameter is ignored.

    The default for this parameter is 15 (poll for all possible ports
    0 through 15). Compaq recommends that you set this parameter to
    the same value on each cluster computer.

    PAMAXPORT is a DYNAMIC parameter.