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

    Specifies a number that identifies the computer. This parameter
    is not dynamic. SCSSYSTEMID is the low-order 32 bits of the 48-
    bit system identification number.

    If the computer is in an OpenVMS Cluster, specify a value that is
    unique within the cluster. Do not use zero as the value.

    If the computer is running DECnet for OpenVMS, calculate the
    value from the DECnet address using the following formula:

    SCSSYSTEMID = ((DECnet area number) * 1024) + (DECnet node number)

    Example: If the DECnet address is 2.211, calculate the value as
    follows:

    SCSSYSTEMID = (2 * 1024) + 211 = 2259

    SCSSYSTEMID has the GEN attribute.