Net Change MRP — Manufacturing Glossary

Net change MRP is an MRP processing method that replans only the items affected by transactions since the last MRP run, rather than replanning the entire product database. By selectively recalculating only what has changed, net change MRP delivers faster plan updates — enabling manufacturers to respond to demand shifts, inventory changes, and supply disruptions within hours instead of waiting for the next weekly regenerative MRP run.

At User Solutions we see net change MRP as the daily heartbeat of responsive manufacturing planning — keeping the plan current between full regenerative cycles.

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How Net Change MRP Works

Net change MRP tracks which items have been affected by transactions and flags them for replanning:

1. Transaction logging — Every event that changes an item's supply or demand picture is recorded: new customer orders, inventory receipts, work order completions, BOM changes, etc.
2. Flagging affected items — The system marks each directly impacted item and its parent/child items for replanning.
3. Selective replanning — MRP recalculates net requirements and planned orders only for flagged items.
4. Cascading through BOM levels — If a lower-level item's plan changes, its parent items are also checked.
5. Generating targeted action messages — Only messages related to changed items are produced.

What Net Change Does NOT Do

Net change MRP does not delete and rebuild the entire plan. Items with no transaction activity retain their existing planned orders unchanged. This is both the strength (speed) and the limitation (potential for accumulated drift) of the approach.

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Net Change MRP Example

A manufacturer runs net change MRP every morning at 6 AM. Since yesterday's run, these transactions occurred:

Net change MRP identifies 47 items requiring replanning (out of 8,000 total):

• Product A and its 12 BOM components — new demand from the sales order
• Steel Bar and 8 parent assemblies — supply changed from PO receipt
• Bearing X and 6 parent assemblies — inventory correction may create a shortage
• Gaskets Y and Z plus Assembly B — BOM change affects material planning

Processing time: 3 minutes (versus 2.5 hours for a full regeneration).

The planner reviews 15 action messages by 6:15 AM and discovers that the Bearing X shortage will delay Assembly C if not addressed. They expedite a purchase order with the supplier and adjust the schedule — all before the shop floor starts at 7 AM.

With only weekly regenerative MRP, this shortage would not have been discovered until the following Monday.

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Why Net Change MRP Matters for Scheduling

Enables same-day responsiveness. Customer changes, supplier notifications, and shop floor events happen every day. Net change MRP translates those events into updated plans within minutes.

Supports real-time scheduling. Scheduling tools like Resource Manager DB perform best with current data. Running net change MRP before the daily scheduling cycle ensures the scheduler works from an updated plan.

Reduces planner overload. Instead of reviewing thousands of action messages from a weekly regeneration, planners see only the changes from the past 24 hours — a far more manageable daily review.

Complements regenerative MRP. The best practice is both: net change daily for responsiveness, regenerative MRP weekly for integrity. They are partners, not competitors.

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Related Terms

• Regenerative MRP — The full-replanning method that cleans up the plan completely, complementing net change's daily updates.
• Planned Order — The order MRP creates or adjusts during net change processing.
• Firm Planned Order — Orders locked by the planner that net change MRP flags but does not modify.

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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.