Planning Flexibility – A Field as Useful as It Is Dangerous

In production projects, I’m often asked whether it’s possible to prevent the planning engine from suggesting changes to purchase or production orders that have already been entered in the system (often manually) and that should not be modified.

While manual order entry is not really compatible with the use of MRP, Business Central provides the Planning Flexibility field, available both on purchase order lines and production order lines.

This field, which is not visible by default and must be added to the page through Personalization, offers two possible values: Unlimited and None.

The default setting is Unlimited, but if you want the planning engine not to suggest any changes to this order line, you can switch it to None.

This setting, as we’ll see, makes the order line fixed and not subject to changes.

At first glance, that might seem to settle the matter, but you need to be very careful — the side effect can be quite dangerous, as I’ll show in the following example.

I’ve manually entered a production order for 200 tables with a due date of February 19, and set Planning Flexibility to None.

In the Item Availability by Periods view, the system correctly shows the receipt of these 200 tables on February 19.

Now let’s suppose that a customer sends us a sales order for 180 tables with a Shipment Date of February 18.

The Item Availability by Periods view shows that, due to a one-day gap between production and sales, we are short of 180 tables.

Naturally, in a situation like this, the first thing to do would be to suggest that the customer receive the goods the following week, avoiding disruption of existing production plans — but we know that this often doesn’t happen.

So, in this scenario, when we run the planning engine, we get the following result:

The system suggests producing 180 tables the day before the expected receipt of the 200, because those 200 tables cannot be considered as candidates for rescheduling the production date.

If we confirm this plan, we would end up in the following availability situation — with 200 tables in inventory that are not used to meet the demand from the previous day.

With the Planning Flexibility field set to Unlimited, however, the planning engine would instead suggest bringing forward the production of the 200 tables by one day and reducing the quantity to 180.

Conclusions

Using the Planning Flexibility field to prevent the planning engine from suggesting changes to existing purchase or production orders can turn out to be quite risky, as it may increase inventory levels even in situations where this could be avoided.

Since the planning engine only generates suggestions for actions to meet demand, it’s probably better to let it propose an action — even one that might not be feasible — so that the planner can still reason about it, rather than not seeing at all an alternative to a supposedly fixed production plan.

©2022–2025 Marco Francesco Ferrari