Planning with iterations

As a rule, the order in which plan items are planned in master planning depends on the phase number of the plan unit that each item belongs to. (If a plan item is not linked to a plan unit, the phase number of the item itself is used). For more information, see Planning sequence and phase numbers.

The normal planning order starts with the lowest phase number, and ends with the highest phase number. LN assigns phase numbers in such a way that a manufactured item is planned before its components are planned. In this way, dependent demand originating from the end item is taken into account when its component is planned.

However, this planning order poses a problem if material constraints are to be considered. Actually, a planning pass in the opposite direction (starting with the highest phase number: first component, then end item) would be the most efficient way to pass on the constraints to higher levels in the bill of critical materials (BCM). After that, a planning pass in the normal direction is needed again, to recompute the consequences of the constraint for all parts of the BCM structure.

For this purpose, the workload-control planning algorithm uses iterations. An iteration is a two-way planning pass, consisting of:

• A reverse planning pass (in order of decreasing phase number: first component, then end item).
• A normal planning pass (in order of increasing phase number: first end item, then component).

For an example, see Planning with iterations, an example.

In principle, one iteration can be sufficient if all items to be planned belong to only one BCM structure. Usually, however, the planning situation is more complex, with different production processes competing for a common resource or for a common component item. In such cases, full optimization of the entire planning requires the use of multiple iterations. In the Generate Master Planning (cprmp1202m000) session, you can specify the maximum number of iterations used for the simulation run.