At the recent AXUG Summit in Reno, I led or participated in a number of sessions discussing master planning. One of the things that seemed to come up in each of them was performance and how to troubleshoot how master planning is functioning. Roxana Diaconu at Microsoft has put together a pair of blog posts detailing a number of specific items that you can check when if you have issues with master planning taking a long time to process. These suggestions should certainly be reviewed by all people that are experiencing long process times. http://blogs.msdn.com/b/axmfg/archive/2014/12/29/checklist-for-improving-mrp-performance-part-1-how-to-run-mrp.aspx http://blogs.msdn.com/b/axmfg/archive/2015/01/02/checklist-for-improving-mrp-performance-part-2-how-to-setup-planning-parameters.aspx Although these tips are great for addressing performance issues, I’ve also heard people struggling to troubleshoot the functional behavior of master planning. Specifically, a couple of people asked questions like “when I get a planned order that doesn’t look right to me, how should I start digging into it” and “MRP isn’t behaving like I expect it should – where can I go to investigate further”.
Net requirements
When I start to dig into master planning behavior, I usually start at the net requirements form. Selecting the released product from “Product information management”–>”Common”–>”Released products” and clicking the “Net requirements” button on the Plan fast tab, the following form displays. 
This form displays the net requirements for an item – all the demand and supply associated with an item. The form is split into 3 parts –coverage dimensions (top), requirements (middle), and pegging (bottom.) As the form is dynamically controlled by the coverage dimensions section, it is important when reviewing the requirements or pegging to first select the appropriate coverage dimensions value. NOTE: Make sure to review the “Setup” tab of the coverage dimensions section to make sure there are not any item-specific coverage settings overriding the selected coverage group. It’s important to understand how an item is supposed to be planned before you start troubleshooting.
Pegging section of the net requirements form
After the appropriate coverage dimensions selection is made, the requirements form is filtered to reflect the selection. In the requirements form, all the demand (such as sales orders or production lines) and the supply (such as production orders or purchase orders) expected to flow in and out of the system are displayed. If you have concerns about why a particular order exists, selecting the order in the requirements section and reviewing the pegging section should help you identify how the requirements relate to each other. 
If the order you’re wondering about is a purchase order, you should fairly easily be able to identify the demand that’s pegged against it and determine why it was generated. If the order you’re looking at is a component of a production order, though, it gets a little more difficult. While looking at the net requirements is great to understand master planning calculations on an item-by-item basis, you have to go elsewhere to navigate up and down the requirements tree to see what upper-level demand is driving the derived requirements.
Explosion form
When the particular derived requirement (or item that’s used in an upper-level BOM) is selected in the requirements section of the net requirements form, click the “Inquiries”–>”Explosion” button. The explosion form shows a graphical representation of all the levels of requirements for a selected order. In this form you can view either the downstream demand generated by the selected order (if the selected order is a produced material) or the upstream demand and supply that ultimately generated the selected order. In the example shown in the screenshot below, by selecting the “Up” principle, it’s clear to see the upper-level sales demand and subsequent parent production order driving the lower-level demand of item M0001. 
This form is somewhat configurable, as well. Although in the above screenshot, only the product name, product number, order number, and reference type are shown, you can add more fields as necessary. For example, if the order date and requirement date are also required, click the “Setup” button and select the “order date” and “requirement date” fields. 
While this adds the date fields desired, it’s not clear which field is which. Clicking the setup button again and adding the “View format explanation” button displays an index in the form which indicates which field is where. 
Explosion trace
If something still isn’t making sense, and you’re using AX 2012 R2 or later, you can try updating the explosion and enabling the trace functionality. From the explosion form, click the “Update” button and make sure the “enable trace” checkbox is enabled on the dialog that displays. NOTE: This needs to happen at the upper-level BOM. NOTE: Updating the explosion will re-calculate net requirements on the full requirements tree. It inserts the results into the dynamic plan selected in the master planning parameters. This may affect other people using net requirements, so it is important to understand this before updating explosions. Once the explosion recalculates, you can view the explanation by clicking on the “Explanation” tab. 
As seen in the screenshot above, a user friendly explanation of what master planning did is displayed and can be used for additional troubleshooting. Still not clicking? Need some more help? Reach out to [email protected] to get in touch!