This message alerts you to a poor coding practice that may require you to edit some of your source code: even under OPT(0), the new compiler will flag any DO loop where the control variable has the PICTURE attribute. The compiler will issue this informational message:
IBM2811I I Use of PICTURE as DO control variable is not recommended.
In general, the use of PICTURE variables as DO loop control variables is a very poor programming practice (especially because it can lead to poor performance), and it would be best to change such code to use FIXED BIN variables as the loop control variables.