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

    RAD_SUPPORT enables RAD-aware code to be executed on systems
    that support Resource Affinity Domains (RADs); for example,
    AlphaServer GS160 systems.

    A RAD is a set of hardware components (CPUs, memory, and I/O)
    with common access characteristics. For more information
    about using OpenVMS RAD features, refer to the OpenVMS Alpha
    Partitioning and Galaxy Guide.