MM / P2Pbeginner

MM MRP Part 1: How Material Requirements Planning Works

Key takeaway

MRP makes sure materials are available on time without excess stock. Learn net requirements calculation (requirements vs stock and receipts), lot sizing, scheduling back from the requirement date, procurement proposals (planned orders, purchase requisitions, schedule lines), and where planners see the result.

What this complete series covers

Learn Material Requirements Planning in a clear, practical sequence — from the basic idea to real project use, troubleshooting, and interview-ready understanding.

Who it is for: Best for SAP consultants, developers, and learners who want a practical understanding of Material Requirements Planning.
Prerequisites: Basic SAP S/4HANA navigation and an understanding of the business process are helpful. Configuration or transaction steps require suitable access to a practice or project system.
Final outcome: By the end, you should be able to explain Material Requirements Planning clearly, follow the main end-to-end flow, apply it in a project scenario, and troubleshoot the most common issues.

Part 1: MM MRP Part 1: How Material Requirements Planning Works
Understand how MRP compares requirements with available stock and scheduled receipts, then creates procurement proposals only for the net shortage within the planning horizon.
Part 2: MM MRP Part 2: MRP Live (MD01N) — HANA-Optimized Planning and Scope
Understand MRP Live as the S/4HANA-optimized planning run that performs major planning calculations on HANA and uses classic logic only where required by unsupported scenarios.
Part 3: MM MRP Part 3: MRP Types, Lot Sizing, Safety Stock and Reorder Point
Understand how MRP type selects the planning method while lot sizing and safety stock determine when shortages arise and how much the system proposes.
Part 4: MM MRP Part 4: Planning Time Fence, Firming and Procurement Proposals
Use planning time fences and firming rules to protect near-term procurement or production proposals from constant MRP rescheduling while allowing the future plan to remain dynamic.
Part 5: MM MRP Part 5: Troubleshooting MRP — Exception Messages, Dates, Sources and Missing Proposals
Troubleshoot MRP systematically by reconstructing one material's stock/requirements list, planning parameters, dates, sources and exception messages before changing master data.

System and release assumptions: Examples focus on SAP S/4HANA. Exact apps, transaction codes, configuration paths, and field names can vary by release and deployment model.

Explanation

📌 KEY POINTS
✅ MRP compares requirements (sales orders, forecasts, dependent requirements) with available stock and fixed receipts.
✅ For a shortage it creates proposals: planned orders (in-house or external) or purchase requisitions, sized by lot size.
✅ Dates are scheduled backward from the requirement date using planned delivery time, GR processing time and in-house production time.
✅ MD04 (stock/requirements list) shows the dynamic situation; MRP controllers work from it and exception messages.
⚠️ MRP is only as good as its master data — wrong lead times and lot sizes produce wrong proposals.

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▶ WHAT THIS SERIES COVERS
Part 1: How MRP works
Part 2: MRP Live (MD01N)
Part 3: MRP types, lot sizing, safety stock and reorder point
Part 4: Planning time fence, firming and procurement proposals
Part 5: Troubleshooting MRP

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▶ 1. REQUIREMENTS

Independent (sales orders, planned independent requirements) and dependent (BOM explosion).

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▶ 2. NET REQUIREMENTS

Requirement − (stock + fixed receipts − safety stock) → shortage.

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▶ 3. LOT SIZING

Exact, fixed, periodic, replenish to maximum.

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▶ 4. SCHEDULING AND PROPOSALS

Backward scheduling; planned orders vs PRs (creation indicator); external procurement uses planned delivery time.

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▶ 5. MONITORING

MD04, MD05/MD06 lists, exception messages.

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▶ STEP BY STEP

Create a sales order for a material with no stock.
Run MRP (MD02 or MD01N).
Check MD04 for the proposal and its dates.

✅ CHECKPOINT: you can explain the quantity and dates of the proposal from master data.

Code example

ABAP Code

===== STEP 1: run =====MD01N MRP Live (plant scope) | MD02 single item, multi-level | MD03 single item, single level ===== STEP 2: example =====Requirement 100 on day 30 | stock 20 | safety stock 10 → shortage 90 → lot size EX → PR 90Planned delivery time 10 days, GR time 2 days → delivery date day 28, release date earlier (purchasing processing time) ===== STEP 3: evaluation =====MD04 stock/requirements list | MD05 MRP list (static) | exception messages

Real project scenario

Support saw no new PR for a shortage and suspected an MRP bug. MD04 showed an old firmed PR covering the requirement, but its date was far too late. Rescheduling the firmed PR (exception message) solved the shortage, and planners were trained to act on reschedule-in messages.

Common mistakes

Ignoring MD04.
Wrong lead times.
Forgetting firmed proposals.
No safety stock logic.
Manual PRs duplicating MRP.

Best practices

Review MD04 daily.
Keep lead times realistic.
Act on exception messages.
Use safety stock deliberately.
Avoid duplicate manual PRs.

Interview angle

Questions: "How does MRP work?", "What is net requirements calculation?", "What is MD04?"
Strong answer: requirements vs stock/receipts, lot sizing, backward scheduling, proposals, MD04 and exceptions.

Practice this lesson

Quick check

1. A shortage exists but MRP creates no new requisition. MD04 shows an old firmed PR with a late date. What is happening?

2. In the context of multi-level BOM planning, why does the MRP run process materials in order of their low-level code?

3. After executing MRP, a planner wants a snapshot of the planning result as it stood right after the run, unaffected by subsequent goods movements. Which evaluation should the planner use?

Interview questions

1. How would you apply Material Requirements Planning in a real SAP project? Walk through the design or implementation approach.

Answer it in your own words first, then compare.

2. Explain how MRP calculates a purchase requisition for an externally procured material.