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

       /SOURCE=device-name:[directory-name]

    Specifies the disk and directory where the utility searches for
    the software product kit or kits. If /SOURCE is not specified,
    the utility searches in the location that the logical name
    PCSI$SOURCE defines. If PCSI$SOURCE is not defined, and the
    /SOURCE qualifier is not specified, the POLYCENTER Software
    Installation utility searches the current default directory.