VMS Help PRODUCT, EXTRACT, PTF, Qualifiers, /BASE_SYSTEM  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /BASE_SYSTEM=base-system-name

    Selects software products whose base system matches the one
    specified. The base system name identifies both a hardware
    platform and an operating system. The base system name AXPVMS
    denotes an OpenVMS Alpha product, VAXVMS denotes an OpenVMS VAX
    product, and VMS denotes a product applicable to either OpenVMS
    Alpha or VAX.