The Copy a Source String Passed by Descriptor to a Destination
    String routine copies a source string to a destination string.
    Both strings are passed by descriptor.
    Format
      OTS$SCOPY_DXDX  source-string ,destination-string
1 – Corresponding JSB Entry Point
OTS$SCOPY_DXDX6
2 – Returns
    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.
3 – Arguments
 source-string
    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor
    Source string. The source-string argument is the address of a
    descriptor pointing to the source string. The descriptor class
    can be unspecified, fixed length, dynamic, scalar decimal, array,
    noncontiguous array, or varying.
 destination-string
    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor
    Destination string. The destination-string argument is the
    address of a descriptor pointing to the destination string. The
    class field determines the appropriate action.