When we start predictive material requirements planning (pMRP), the first step in the process is to create the pMRP simulation.
PMRP Compared to LTP
If we compare pMRP with SAP S/4HANA with long term planning (LTP), this step is somewhat similar to the creation of a long-term planning scenario; the difference is that the long-term planning scenario is created for a whole plant, whereas we can choose a restricted set of master data for our pMRP simulation. When we create the simulation, we select which top-level materials or work centers will be considered for pMRP.
Another difference between pMRP and LTP is that all the planning will happen during the simulation creation itself, whereas in LTP we first release the planning scenario and then execute the planning run (as many times as we want). In pMRP, we will be able to process the simulation immediately after the creation is finished and will not need to wait for a planning run.
A third difference is that whereas LTP generally runs with the same MRP type and lot-sizing procedure used by operational MRP, pMRP uses a simplified planning logic, in which all materials will use a deterministic MRP and a lot-for-lot procedure.
Creating a pMRP Simulation
Before the creation of the simulation, we need to ensure that the relevant master data has been created. It is also important to have planned independent requirements (PIRs) created: they will be the main input for the pMRP simulation. The system will plan the selected materials and determine the work center capacity requirements based on those PIRs.
Warning: When a simulation is created, master data will be copied into it, so subsequent changes to master data may not be considered.
The pMRP simulation creation is basically a background job that can be scheduled through the Schedule pMRP Simulation Creation app (see the application tile in the figure below). This application can also be used to manage background jobs that are already finished, scheduled, or in process.
As shown in the next figure, an icon will be shown in the Log column with the status of the finished background executions, and another icon is shown in the Results column. By clicking the icon in the Log column, we will jump into the job log, which will show the details of success, warning, or error messages that may have been triggered during each step of the simulation creation.
The next figure shows the details of the simulation creation logs, including the success and error messages being triggered. When clicking the icon under the Results column, we will jump into the spool, where we will find a list of the materials and work centers selected for the simulation.
We can create, copy, and delete a simulation creation (although deletion is only possible for scheduled jobs). During the creation of a new job, we can choose between two different job templates and, depending on the selection in the Job Template field, we will have different criteria.
Creation of pMRP Data via Top-Level Materials
Object selection is based on the material master, so selection criteria will be focused on the material master information, such as material number, MRP controller, or low-level code. The system will look for PIRs for the pertinent materials and run simplified MRP to determine the required quantity for each level and the capacity allocated in the work center.
Creation of pMRP Data via Work Center
Object selection is based on the work center, so the selection criteria will be focused on the work center. The system will look for capacity requirements in the selected work centers and then identify the top-level materials and the respective PIRs.
The next figure shows the creation of a new pMRP simulation based on the top-level materials and shows the job template selected. In the Scheduling Options section, we can define whether the job will be executed immediately or scheduled to run on a future date.
Note: The creation of the pMRP simulation will be executed only once; therefore, it should not be executed as a periodic job, and the Recurrence Pattern value is set to Single-Run by default.
In the Parameter section, we fill the ID for Reference Plan and Simulation ID fields, which are used to identify the simulation. These should be unique values; the reference ID and simulation ID cannot be the same. The ID for the reference plan will represent the set of master data selected according to the selection criteria, and new simulations can be added later under the same reference ID. Under the Parameter section, we also need to select the bucket category (daily, weekly, or monthly buckets) and the start and end date for the simulation.
Under the Limits sections, we will find fields that can be used to restrict the selection. We can use those fields to ensure that pMRP will be executed only for materials with a specific BOM, routing, or material status, or for a BOM or task list usage. The Object Selection section contains the fields we will use to select the materials or work centers. Depending on the job template selected, we will see material-related fields (such as the Material, Plant, MRP Controller, Material Type, or Low-Level Code) or work center-related fields (such as Work Center, Work Center Category, or Person Responsible). We can also define if we will consider stock transfers in the scenario and which plants and which work centers from those supplying plants should be considered in the simulation.
Finally, under the Document Data section, we can choose if the opening stock will be zero, if it will be the safety stock or the actual material stock at the plant, if we will consider an inactive PIR version instead of the active version, and if the simple discontinuation will be considered.
Note: All those settings are defined in the reference plan during the simulation creation. They cannot be changed later when we are adding new simulations into the same reference plan.
Once we click the Schedule button, the background job to create the new simulation will be scheduled. Depending on the number of materials selected for the simulation, it may take some time because an actual planning run is being executed. We will see the simulation creation logs and the spool after the execution.
Editor’s note: This post has been adapted from a section of the book Material Requirements Planning with SAP S/4HANA by Caetano Almeida.