RO,
Standard PP/DS material planning and capacity planning are also normally taken as separate steps as well. Only using optimizer or CTM can you consider material constraints (MRP type planning) and capacity constraints simultaneously in a single solve.
ECC currently has no equivalent of optimizer or CTM. In ECC (and in PP/DS) you solve for one type of constraint (material shortages), then you solve for the other type of constraint (capacity shortages). In all cases, when you solve for capacity after creating the solution for material shortages, it tends to degrade the quality of the material solution.
Best Regards,
DB49