Creating a Predictive MRP Simulation with SAP S/4HANA

When we start predictive material requirements planning (pMRP), the first step in the process is to create the pMRP simulation.

Scheduling a pMRP Simulation Creation

The main input for pMRP is the forecast—that is, PIRs. Therefore, before the actual creation of the pMRP simulation, you should ensure that you have created PIRs. In addition to the PIRs, pMRP also can consider sales order demands for the finished products as inputs for the simulation creation.

If you want to create PIRs that will be relevant for pMRP but not for operational MRP, you can create inactive PIRs. pMRP can work with both active and inactive PIRs, and you’ll be able to choose the ones to consider during the simulation creation.

When you create a pMRP simulation, the necessary master data is selected, and the relevant information is copied to the simulation and simplified. This means that if you change master data after the simulation creation, the simulation will not reflect this change. The same is valid for transactional data, such as PIRs or sales orders.

Note: As of SAP S/4HANA 2022, you can refresh the reference data to update the pMRP simulation with changes made after the simulation creation.

After copying the master data, pMRP will execute the simulated planning run, calculating the required quantities, selecting the sources of supply, exploding BOMs, and determining capacity requirements. As mentioned earlier in this chapter, pMRP executes a simplified planning run because all materials will be planned with a deterministic MRP (similar to PD), and a lot-for-lot (similar to EX) procedure will be used to calculate the quantities. Even a material with a reorder point MRP type set at the material master will be planned with a deterministic MRP. In addition, most of the MRP settings defined in the material master, such as a minimum lot size and other settings that affect the lotsizing calculation, aren’t considered in the pMRP calculation.

The pMRP simulation is created using the Schedule pMRP Simulation Creation app, in which you can schedule a background job to create the simulation. This step is executed in a background job because, depending on the volume of data selected, it may take some time to complete the simulation creation.

When you enter this app, you can see a list of the recently completed jobs by clicking the Go button, as shown in the figure below. By selecting a line and clicking the Details button, you can see the details of a simulation, such as the scheduling options, the run details, and the input parameters. Under the run details, you can also branch into the job spool, where you’ll find the complete list of products and work centers selected for the simulation. Here you can also cancel a simulation that is still in progress, or restart a simulation by selecting it and clicking the respective buttons.

You can create a new pMRP simulation by clicking the Create button, or by selecting an existing simulation and clicking the Copy button. You can also choose to Restart or to Cancel a simulation that is running.

There are three steps in the simulation creation: performing the Template Selection, defining the Scheduling Options, and setting the simulation Parameters. Let’s go through the steps to understand each one.

Template Selection

In the Template Selection step, choose which Job Template to use in your simulation and what the Job Name will be, as shown in the next figure. Selecting the correct Job Template is very important, as the template will dictate how pMRP will select data to create the simulation.

pMRP offers the following standard job templates for the simulation creation:

• Creation of pMRP Data via Top-Level Materials: If you select this option, pMRP will consider that the selection parameters provided later will refer to top-level materials; therefore, it will try to find demands (PIRs or sales demands) for the selected materials. Whenever it finds demands for a top-level material, it will plan all the levels of components accordingly.
  
• Creation of pMRP Data via Components: Select this template when you provide parameters to select components as inputs for the simulation creation. In this case, pMRP will use the BOM to find the relevant upper-level materials, and it will look for demands for those materials.
  
• Creation of pMRP Data via Work Centers: When using this template, pMRP will require parameters to select work centers as an input for the simulation. pMRP will then find on which routings those work centers are used, and it will try to find demands for the respective materials.

Example: If you select the Creation of pMRP Data via Top-Level Materials template and you provide raw materials as an input for the simulation, pMRP will probably not be able to generate a simulation, as you don’t usually have sales orders or PIRs for raw materials. But if you choose the Creation of pMRP Data via Components template, pMRP will first try to find in which BOMs those raw materials are used and then find the respective top-level materials. In this case, it will probably find demands for the top-level materials, and it will be able to create the simulation.

Scheduling Options

The second step to create a pMRP simulation is to define the Scheduling Options, as shown in the next figure. Here you’ll choose when the background job will be executed and how many times it will be executed. When you reach this step in the simulation creation, the Start Immediately flag is checked by default, which means that the background job will start as soon as you input all the parameters and confirm the simulation creation. If you uncheck this flag, the Start and Time Zone fields will be then open for input, and you can choose a date in the future for the simulation creation.

If you select the Define Recurrence Pattern option, a popup screen will be displayed where you can schedule a periodic execution of the background job. For example, if you know that a new forecast is created for your finished products every month, you can also schedule the creation of a new simulation every month, as shown in the figure below. In this way, users won’t have to worry about creating a new simulation whenever a new forecast is uploaded into the system.

Parameters

The third and final step is the most important of the pMRP simulation creation. This is when you’ll define the selection parameters and the restrictions available for product selection and for the work centers that can be parts of the simulation. The figure below shows an overview of the Parameters step, in which you can see different sections containing all the fields available for your top-level material simulation.

Note: Different parameters will be available for the selection, depending on the template selected. For example, if you choose the Creation of pMRP Data via Work Centers template, you’ll have the Work Center as the selection parameter instead of the Material.

Let’s walk through each section of parameters:

• Reference and Bucket Definition: Under the Reference and Bucket Definition section, you’ll find the ID for Reference Data field, which will represent the set of master data selected according to this specific criteria. You also have the Bucket Category, in which you can choose whether the simulation will be created in monthly or weekly buckets, and the start and end dates, which will restrict the selection of demands that you’ll use to build the simulation.
• Simulation Name: You’ll find the Simulation ID field under the Simulation Name section, which will uniquely describe this simulation.
• Limitations: The Limitations section brings several selection parameters that you can use to limit the master data selections, including the material, the BOM and routing status, the BOM and task list usage, and the capacity category.
• Object Selection: Fields available under the Object Selection section can vary depending on the template previously selected for the simulation. For example, if you decided to create the pMRP data using the template for top-level materials or components, you’ll see fields mainly related to the material master in this section, such as the Material, the MRP Controller, the Material Type, or the Low-Level Code. If you choose the template to create the pMRP data via work centers, you’ll see fields mostly related to the work center in this section, such as the Work Center, the Work Center Category, or the Person Responsible. Under the Object Selection section, you’ll find the Additional MRP Types field, no matter which template you select for the simulation. As mentioned in the previous section, you can use this field if you want to include materials that MRP does not plan in the simulation, such as materials that use MRP type ND, for example.
• Stock Transfer Behavior: The Stock Transfer Behavior section includes fields that can include additional plants involved in a stock transfer scenario, either supplying components or consuming products from the plants selected in the simulation. Whenever the Stock Transfer from/to Plants flag is marked, you’ll be able to select which additional plants and work centers to consider for the simulation when part of a stock transfer scenario.
• Document Data: Finally, the Document Data section introduces fields related to the transactional data that should be considered in the simulation. You can use the Opening Stock field to choose whether pMRP will not consider any opening stock for the simulation, whether it will use the safety stock, whether it will use the stock on the current date, or whether it will use the stock projected for the simulation start date as the opening stock. You can use the Consider Inactive PIRs field if you want to include inactive PIRs in the simulation, and you will have to input which versions to consider in the Consider Inactive PIR Versions field. This option is particularly relevant when you need to validate a forecast using pMRP before releasing the PIRs for operational MRP. Similarly, you can use the Ignore Active PIRs field if you want to ignore particular versions of active PIRs. This option is generally used when you want to consider an inactive PIR version instead of the active one.

pMRP will consider sales order demands by default as an input for top-level materials, but you can ignore this kind of demand by checking the Ignore Sales Demands flag. When this flag is marked, pMRP will consider the PIRs as the main input for the top-level materials when creating the simulation. Finally, pMRP can also consider discontinuation and include the follow-up material of discontinued materials in the simulation if you mark the Consider Simp. Discontinuation flag. The Determine Prod. Time f. Lotsize flag can be used if you want to consider the lot size–dependent production time that you define in the Work Scheduling tab of the material master, instead of the lot size–independent production time that you define in the MRP2 tab.

Once you finish the input, click the Check button to verify whether all your inputs are correct, or click the Schedule button to trigger the scheduling of the pMRP simulation creation. You can use the Template button to save your inputs as a template that you can use to create other simulations in the future or to load previously saved templates. You can use your own templates to create a simulation instead of the three standard templates mentioned earlier in this section.

Evaluating the Simulation Creation Logs

After creating the pMRP simulation, let’s go back to the initial screen of the Schedule pMRP Simulation Creation app, which you previously saw.

All the jobs that are in process, scheduled, or finished will be listed here, so long as they are within the time interval defined in the Date From-To field. The Log column contains icons with the job log status for all the finished jobs, informing you whether there were only information messages , whether there were warning messages , or whether there were error messages . By clicking these icons, you can see the detailed log of the pMRP simulation creation.

If you select one of the simulations and click the Details button or simply click the arrow at the end of the line, you’ll see the simulation details, including the scheduling options, the run details, and the parameters used to create the simulation. In the simulation details, you also will see the log status containing a detailed simulation log.

The next figure shows an example of a pMRP simulation creation that was concluded, but with warning messages. In this example, the simulation creation’s detailed log shows that there was no routing in the production version of two materials included in the simulation. This means that pMRP could not create capacity requirements for those materials.

By clicking the file icon, which is found in the Results column (refer to Figure 12.13), you’ll be redirected to the background job spool. For each background job, you should find two different spool requests: one will show a list of all the materials included in the simulation, and the other one will open a list of all the work centers included in the simulation.

The next figure shows the spool request for a pMRP simulation with the list of selected materials. The Excl. Obj. column is marked for some materials, which means that they were excluded from the simulation, even though they were selected according to the selection criteria defined when creating the simulation. You can find the reasons for the exclusion of those products from the simulation under the Comment column; in this specific case, we did not find any top-level demand for these products, meaning that there was no PIR or sales demand for the top-level product.

Learn more about logistics with SAP S/4HANA here.

Editor’s note: This post has been adapted from a section of the book Material Requirements Planning with SAP S/4HANA by Caetano Almeida.