Maybe this is what you are trying for:<pre>
dow NOT %eof(master) and x <= 600;
%subarr(arr1:x:3) = artypes;
x += 3;
Those changes are all inside of your original DOW loop.
The D-specs need this change:<pre>
D type1 3a
D type2 3a
D type3 3a
D artypes 3a dim(3) overlay( types )</pre>
By including an array definition overlaying the DS, the %SUBARR() becomes available. The function copies an array (or portion of an array) to a portion of another array (or to an array). IOW, it needs an array reference on both sides of the equation.