/sys$common/syshlp/helplib.hlb DCE_IDL, DCL Command Interface, QUALIFIERS, /OPTIMIZE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

      /OPTIMIZE [=({SPEED | SPACE })]
      /OPTIMIZE = SPEED (default)

        This qualifier is equivalent to the -space_opt
        argument in the universal syntax.