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

    OpenVMS usage:word_unsigned
    type:         word (unsigned)
    access:       write only
    mechanism:    by value

    Number of bytes not moved to the destination string if the length
    of source-string is greater than the length of destination-
    string. The value is 0 (zero) otherwise.