Regenerative MRP — Manufacturing Glossary

Regenerative MRP is an MRP processing method that completely replans every item in the product database during each run. It deletes all existing planned orders, re-explodes every BOM, recalculates all net requirements, and generates a fresh set of planned orders from scratch. It is the most thorough — but also the most computationally intensive — form of MRP processing.

At User Solutions we recommend regenerative MRP as the weekly "clean sweep" that ensures plan integrity, complemented by net change MRP for daily responsiveness.

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How Regenerative MRP Works

A regenerative MRP run follows these steps:

1. Delete all existing planned orders throughout the system.
2. Read the Master Production Schedule for all finished goods.
3. Explode every BOM level by level, from finished goods down to raw materials.
4. Calculate gross requirements for every component in every time bucket.
5. Net against inventory and scheduled receipts for every item.
6. Apply lot sizing and lead-time offsets to generate new planned orders.
7. Generate exception messages — action alerts for the planner.

The key characteristic: every item is replanned, whether it changed since the last run or not. This ensures complete consistency across the plan but requires significant processing time.

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Regenerative MRP Example

A manufacturer with 8,000 active part numbers and 3,200 BOMs runs regenerative MRP every Sunday night:

Before the run:

• 4,500 planned orders exist in the system from last week's run
• 340 new sales orders entered during the week
• 85 purchase orders received (completed scheduled receipts)
• 12 engineering changes modified BOMs
• 25 inventory adjustments from cycle counts

During the run (processing time: 2.5 hours):

• All 4,500 existing planned orders are deleted
• All 3,200 BOMs are exploded against current demand
• All 8,000 items are netted against current inventory
• 4,680 new planned orders are generated
• 320 action messages are produced (expedite, defer, cancel recommendations)

After the run:

• The plan reflects every change from the past week — not just the ones flagged by transactions
• Any inconsistencies from partial updates during the week are eliminated
• Planners review action messages Monday morning and make decisions

Without the full regeneration, subtle issues could accumulate: a BOM change that did not trigger lower-level replanning, an inventory adjustment that was not reflected in a planned order, or a scheduled receipt completion that left orphaned demand.

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Why Regenerative MRP Matters for Scheduling

Ensures plan integrity. Regenerative MRP is the only method that guarantees every item's plan is consistent with current data. This is essential for maintaining trust in the planning system.

Catches cascading effects. A single change — a new customer order, a BOM revision, an inventory correction — can cascade through dozens of BOM levels. Regenerative MRP traces every cascade completely.

Cleans up accumulated errors. Net change runs handle most daily transactions, but edge cases can cause small plan errors to accumulate. Weekly regeneration clears these.

Provides a stable planning baseline. Scheduling tools like Resource Manager DB work best when operating from a clean, comprehensive MRP output. Running regenerative MRP before the weekly scheduling cycle provides that foundation.

Generates comprehensive action messages. The full run produces a complete set of planner recommendations — not just changes since the last run. This is especially valuable for reviewing the overall plan health.

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Related Terms

• Net Change MRP — The selective MRP method that replans only items affected by recent transactions, offering faster but less comprehensive updates.
• Planned Order — The order recommendation that regenerative MRP creates fresh during each complete run.
• Closed-Loop MRP — The planning framework that uses regenerative or net change MRP as its core planning engine.

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FAQ

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This term is part of the Manufacturing Glossary. For a deep dive into material planning, see our MRP Guide.