/sys$common/syshlp/helplib.hlb PRODUCT, INSTALL, 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 defined by the logical
    name PCSI$SOURCE. If PCSI$SOURCE is not defined, and the /SOURCE
    qualifier is not specified, the POLYCENTER Software Installation
    utility searches the current default directory.