PP MRP Why used Planning tools like APO or I2?

APO and I2 are Finite PLANNING tools. When MRP runs with APO or I2 (or Red Pepper or Manugistics), it takes Capacity issues into consideration. MRP in SAP R/3 Core does not, it assumes infinite capacity available. (MRP only looks at material availablity.)

However, SAP R/3 DOES do finite SCHEDULING, which is where the system 'dispatches" operations on a production order until it fills up the capacity available, then moves to the next time period and dispatches until that period is filled up. In SAP speak, that is called capacity leveling.

I believe APO should only be used in very large companies (billions) because of the amount of master data that must be maintained, and that data better be ACURATE, or you've wasted a heck of a lot of time. By the way, APO stands for Advanced Planner and Optimizer tool, obviously a German sort of name!

Differences between planning and scheduling, finite and infinite

R/3 does planning without consideration for capacity situations. So if MRP says you need 500 parts on 3/1/04, it schedules them all to be built at the same time, even though you can only do 100 at a time. Assume you have a fixed lot size of 100, you'll get 5 planned orders for 100 to start on the same day. This is "Infinite Planning". APO would recognize that constraint, and instead schedule out the 5 orders over time. The important part of that is that it also will schedule out the deliveries of the components for 5 different days. This is "Finite Planning".

Now, assume old fashion MRP. It schedules all 5 orders for the same day, and the buyers go out an get all of the components for the same day. Then the planner realizes he can't do all 5, and manually changes the schedule, and manually spreads out the 5 orders. The buyers will recieve rescheduling notifications, but not until the scheduler does the manual rescheduling. You could call this "Infinite Scheduling", but that only means the same thing as Infinite Planning.

But, SAP has "Capacity Leveling". What that means is you run another program after MRP (CM27 and CM28), which can be run in batch mode overnight. (There is a ton of configuration and thinking that will be required to do this!). The capacity leveling program will recognize the constrant at the work center level, and fill up the first day, then re-schedule the next order to the next available capacity, then the next order searches for available capacity, and so on. This is called "Finite Scheduling". The problem with this is the opposite of Infinite Planning, which is it doesn't take Material availablity into consideration! The system will re-schedule a production order without thinking about whether the materials will be available or not.

Finite Planning does Finite Sheduling at the same time. If there is no capacity available on the desired date, the system looks for when capacity IS available. Then it stops to see if Materials will also be available (usually based on the lead-time for those components). If there is a material problem, then the system figures out when the materials WILL be available, and then
checks to see if capacity is available on THAT day, and if so, it blocks off capacity, and allocates the materials for that day.