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2321198 - MRP Troubleshooting Guide

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Symptom

You use MRP for purchasing, production or other logistic processes and analyze the MRP results.

Reproducing the issue

Scenario:

  1. Go to MRP → MRP Wizard.
  2. Fill in the relevant parameters within all fields of MRP Wizard Steps 1 - 6.
  3. Choose the Run button and verify the MRP results.

Actual behavior:

MRP Recommendations expected by the user are not shown.

or

MRP Recommendations not expected by the user are shown.

Cause

Functionality description

Solution

This SAP Note aims to provide you with best practices on how to analyze MRP scenarios in order to gain better understanding of the MRP calculations and MRP results.

Follow the 4 steps below in order to gain better understanding of the MRP output:

  1. Understand the demand sources and BOM Structure.

Is the item in question a Bill of Materials (BOM)? Is it BOM parent item? Or is it BOM component? Is it both parent and component item?

In order to verify the BOM structure, we recommend you to run the Bill of Materials Report for all items. (Production → Production Reports → Bill of Materials Report). You can export the result of this report into Microsoft Excel in order to enable quick search and orientation. You can locate your item, if it is a parent item you can locate the components of this item, if it is a child item, you can locate the parent items, also grandparent items, and so on.

What are the documents that are creating demand and supply for your item and how to check this?

Display the Available-to-Promise report that you can look up via right-click from the Item Master Data.

Please note that not all demand sources are shown in the Available-to-Promise report. Examples of such sources not listed there, are: Minimum quantity, Forecast, both of which can be related not only to the item itself, but also to BOM parent, grandparent.

  1. Simplify the scenario in order to focus your analysis in the right direction.

Start with minimal volume of data such as - choose only 1 item, 1 day or week, one type of demand documents, or even one specific demand document, for example a Sales Order. 

Work on a test system, in order to allow changing existing master data and transaction data, such as closing or canceling unnecessary demand and supply documents, or changing any MRP-relevant settings.

Instead of running the MRP Wizard for the whole company, run MRP only for the relevant item or items. This will enable much quicker testing since the MRP run will not take minutes, but seconds.

Only once you understand the MRP run with limited set of data, you can go ahead and step by step add more complexity (for example, add more document types, items, time periods).

Repetitive testing is really the key in the analysis of any MRP scenario.

  1. Proceed with testing and rerun the MRP Wizard several times, while changing one MRP relevant parameter at a time.

There are number of settings that may affect MRP Results.

We recommend changing only one MRP relevant setting at a time, and proceed again with MRP run, in order to verify if results are affected, or not.

Some of the MRP settings and their dependencies are listed below; you can also check the document How To Configure and use MRP on the SAP Help Portal.

  1. Which MRP settings should you inspect? What are their dependencies? 
  • Settings on Item Master Data:
    • Order Interval
    • Order Multiple
    • Minimum Order Quantity
    • Lead Time
    • Tolerance Days
    • If the Minimum Inventory Level is selected and the Manage Inventory by Warehouse setting is checked on Item Master Data, then all recommendations from MRP will guarantee that there is inventory in the warehouse.
    • Please note that the warehouse option Locked on the Inventory tab is not considered by the MRP Module.
    • Phantom Item - A phantom item is similar to an assembly bill of materials; therefore, it cannot be defined as an inventory item and is not included in the MRP recommendations. Specific rules on warehouse assignment of Phantom child items are described within SAP Note 1732347
  • Other settings
    • Price List on the suppliers (business partner) Payment Terms tab - for example, if you have the wrong currency when creating a Purchase Order based on MRP, the price list currency may be the cause.
    • Week Numbering definition, Weekend definition and Holiday Dates are used by MRP and defined in Administration → System Initialization → Company Details → Accounting Data → Holidays → Holiday Dates.
    • General Settings → Inventory tab → Items tab → Display Inactive Items In. This setting will affect the MRP Wizard demand for specific items which are inactive or are linked to inactive items.
    • When Inventory Transfer Request is created via MRP, the default warehouse set for the item is disregarded. Instead, for the field From Whse in the MRP Results window, the system will select the warehouse with the highest quantity in stock.
  • Scenario Details- MRP Wizard Step 2
    • Cumulative Lead Time - In case documents are not suggested by MRP, you can check whether Cumulative Lead Time is selected or not.
    • You might need to compare Tolerance Days versus Lead Time. When the document is not created by MRP, it is possible that there is no tolerance day defined.
    • When the option Ignore Cumulative Lead Time is checked, the Lead Time will be taken from the main item without considering the Lead Time for the child items.
    • View Data in Periods of: if you choose to group MRP results into period lengths other than one day, SAP Business One performs the MRP calculation on the first day of each period. MRP groups all the existing data for that period (supplies, demands, forecast) in its first day. 
  • Item Selection- MRP Wizard Step 3
    • Only items with Planning Method - MRP will be considered.
    • Several columns are available for display and selection via the Form Settings that may help you in the analysis. 
      You can also select items by, for example, preferred vendor and UDFs from Item Master Data.
    • When a Bill of Materials (BOM) parent is included in the MRP Wizard, all parent's components will be considered in the MRP Wizard regardless of the selection specified in the MRP Wizard.
    • When a Bill of Materials (BOM) component is included in the MRP Wizard, all the BOMs with that component will be considered in the MRP wizard regardless of the selection specified in the MRP wizard.
    • When exploding the BOM in MRP, the system will always look at all demands affecting any BOM component.
  • Inventory Data Source- MRP Wizard Step 4
    • Since version 9.1 the Minimum Level is no longer subtracted: MRP Wizard uses the specified Minimum Inventory Level as a demand in MRP calculation to ensure that the required inventory level is available for unexpected orders. In order not to consider inventory level requirements in the calculation, leave this field blank.
    • In case you do not select the whole company, consider selecting the Inventory Transfer Request in the next step in order to enable replenishing the required inventory between warehouses.
  • Documents Data Source - MRP Wizard Step 5
    • The option Include Historical Data means that all demands and supplies before the start date are considered in the MRP calculations. 
      Recommendations are summed up and displayed in the system date column.
    • The MRP calculation considers only Production Orders with the status "Planned" or "Released". 
    • If a Sales Quotation does not appear in MRP, you should verify whether the Delivery Date is populated in the document.
    • If a Sales Blanket Agreement is not reflected in the MRP Wizard calculation as a source of demand, you should verify that the warehouses are defined at row level in the Sales Blanket Agreement.
    • Required / Minimum / Maximum inventory levels - Replenish items up to the chosen inventory level.
      "Minimum - Maximum" inventory level - this setting will replenish items up to the maximum inventory level, but only when they fall below the minimum inventory level.
    • Options available for Forecasts:
      • You can select multiple MRP Forecasts for MRP recommendations; in addition, MRP forecasts support zero-quantity items.
      • The past requests in forecasts will not be considered by the MRP Wizard. For example, a monthly forecast is defined requiring quantity 10 for each month of the current year. Today is the 5th of April and you run the MRP Wizard. The system will not demand quantity for April but only quantity for May onwardsregardless of the earlier MRP Wizard Horizon - that is even if the Start Date of the MRP Planning Horizon is the 1st of April or earlier. The same logic applies when considering a weekly forecast in the middle of the week.
      • You can create and maintain forecasts for items per warehouse.
      • If a forecast is not considered in the MRP results as expected, this can be caused by the fact that the Forecast is not selected or the Days Backward / Days Forward are not correctly defined. These settings can be found under Administration → System Initialization → General Settings → Inventory tab → Planning subtab.
      • MRP presents forecast requirements only for quantities that have not yet been ordered; only the net forecast quantity is added to the requirements.
    • In case MRP was not run for all warehouses, you might receive a warning window: Production Orders and Stock Transfer Request were not recommended for X parent items due to components that are required from X warehouses whose demand has not been included in this MRP run (for example, XYZ in warehouse XY). You should always be careful when seeing this warning window, as it means that you might miss to produce or deliver in time! The warning means the following: in case a Production Order exists, for which its Item Child’s warehouse is not included in the MRP Wizard, that Production Order will not be considered in the MRP Wizard, even if the Parent’s warehouse is included in the MRP Wizard. 
  • MRP Results - MRP Wizard Step 6
    • BOMs and Future Data in MRP Planning
      Example 1: When inspecting parent item demands in a future period that is beyond the planning horizon, the MRP takes these demands into consideration to calculate order recommendations for the child items involved. However, in the final result, the MRP generates only order recommendations within the planning horizon.
      Example 2: When the MRP cannot create order recommendations in time to satisfy the demands due to the lead time required, the MRP adjusts the order recommendation to the earliest and possible date within the planning horizon.

        For demonstration of the above examples please kindly refer to the Online Help:

        Go to Help → Documentation → Online Help, or open an SAP Business One window and press F1 and search for: Examples: BOMs and
        Future Data in MRP Planning.

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