2.4 MRP parameter governance

Material Requirements Planning (MRP) is a deterministic engine. It calculates supply execution directly based on the variables configured in the Item Master. If the Minimum Order Quantity (MOQ) is inaccurate, the system may generate excess stock. If Safety Stock levels are set arbitrarily, the supply chain may oscillate between line-down shortages and excess inventory. Parameters act as the control mechanisms of your supply chain. Uncontrolled modifications by individual planners can destabilize the procurement signal across the enterprise.

Parameter architecture & ownership

To maintain system integrity, write access to specific ERP parameters must be segregated by function. Clear ownership ensures data accuracy.

Commercial constraints (supplier-defined)

• Parameters: MOQ, Order Multiple (Pack Size), Standard Cost.
• Owner: Sourcing / Procurement.
• The Source: Vendor Contract or valid Quotation.
• The Protocol: These values must mirror physical reality. If a vendor sells components in reels of 1,000, setting the ERP Order Multiple to 1 will likely cause receiving discrepancies or rejected POs.

Strategic buffers (internal risk strategy)

• Parameters: Safety Stock (SS), Reorder Point (ROP), Target Days of Supply.
• Owner: Planning / Supply Chain Manager.
• The Source: Statistical calculation based on historical demand volatility (σdemand) and measured lead time variance (σ_LT).
• The Protocol: These act as financial levers. Significantly increasing Safety Stock requires working capital approval from Finance.

Planning policies (mathematical logic)

• Parameters: Order Policy (e.g. Lot-for-Lot vs. Fixed Period Supply), Shrinkage/Yield Factor.
• Owner: Master Scheduler.
• The Source: Driven by physical production methodology (e.g. Batch Manufacturing vs. Continuous Flow) and historical yield data.

The change control protocol

Avoid changing parameters based on intuition or isolated incidents. Parameter changes should be driven by data.

The “evidence” guideline

Significant supply chain parameter changes (e.g. > 10%) should be supported by documented sources.

• Valid Evidence: A formal Supplier Quote, an Engineering PCN (Product Change Notification), or a proven change in the consumption rate (Rolling Quarterly Average).
• Invalid Evidence: Unverified assumptions or speculative sales projections not reflected in the formal forecast.

Decision logic: when to trigger a system change

When Demand Volatility Statistically Increases:

• Recalculate the Safety Stock.
• Ensure the formula covers the new variance, not just the arithmetic average.
• If the resulting capital requirement exceeds defined thresholds, seek formal Finance approval before updating the system.

When the Supplier Imposes Allocation:

• Update the Lead Time and consider switching the Order Policy to “Fixed Period”.
• Batching small orders into larger scheduled buckets can sometimes secure better production slotting at the vendor’s facility during allocation.

When the MOQ exceeds 6 Months of Historical Demand:

• Flag the item for Engineering Review.
• The financial carrying cost and obsolescence risk of this inventory might justify the NRE cost of redesigning the PCBA to use a more readily available component.

The parameter change log (auditability)

Maintaining an audit trail is essential for understanding why specific inventory levels exist.

Maintain a “Parameter Change Log” (via system tracking or a controlled document):

Date	Part Number	Parameter	Old Value	New Value	Reason Code	Approver
10/24	RES-0402-1K	MOQ	5,000	10,000	Vendor PCN (New Reel Size).	J. Doe
10/25	MCU-STM32	Safety Stock	0	500	New Customer Contract (Risk Buy).	S. Smith
11/01	CONN-USB	Order Policy	L4L	Fixed (4 Wks)	Freight Consolidation strategy.	Director

Pro-Tip: Restrict edit access to the “Order Multiple” field in your ERP to Procurement only. If a part comes on physical reels of 3,000, the system must enforce ordering in those multiples to prevent orphaned inventory errors in the Warehouse Management System (WMS).

Governance cadence (data maintenance)

Parameter data requires routine reviewing to prevent data rot from impacting MRP accuracy.

1. Quarterly Review (The “Sweep”):
   • The Action: Compare current ERP MOQ/LT parameters against recent physical receipts.
   • The Logic: If Procurement consistently orders 5,000 units to secure a price break, but the system MOQ is set to 1,000, update the system to 5,000 to align with actual commercial practice.
2. Annual ABC Re-Classification:
   • The Action: Re-rank all active items based on current trailing 12-month spend and volume.
   • The Logic: An item that was “Class C” last year might be “Class A” today due to volume shifts, requiring its Safety Stock policy to be adjusted accordingly.

Final Checkout: MRP parameter governance

Control Point	Engineering Requirement	Target Goal
Segregation	Sourcing owns MOQ; Planning owns Safety Stock.	Active Access Control
Physical Integrity	System multiples match physical Pack Size.	Verified periodically
Audit Trail	Change Log maintained for significant edits.	Maintained
Finance Gate	Total Inventory Value Increase Approval.	Defined threshold applied
The Evidence	Hard data source cited for system change.	Required
The Cadence	Parameter Review executed regularly.	E.g. Quarterly