VMS Help RTL Routines, STR$, STR$ANALYZE_SDESC_64, Returns  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    OpenVMS usage:quadword_unsigned
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by value

    Length of the data. The return value is the same value returned
    to the integer-length argument.