The ERP Isn't the Problem
When inventory performance deteriorates — stockouts increase, excess builds up, planners stop trusting the system — the instinct is to blame the software. The ERP is outdated. The MRP logic is wrong. We need a new system.
In most cases, that diagnosis is incorrect. The ERP is almost always doing exactly what it was configured to do. The problem is that it was configured once, years ago, and the business has changed significantly since then — while the planning parameters have not. The result is a system generating the right answer to the wrong question. Perfectly executed logic, built on stale assumptions.
What Are Planning Parameters?
Planning parameters are the data fields in your ERP or MRP system that tell it how to plan each item:
- Reorder point (ROP) — the inventory level that triggers a new order
- Safety stock — the buffer quantity held to protect against demand and lead time variability
- ABC/XYZ classification — how the system categorizes each item by value and demand predictability
- Lead time — how long it takes from order placement to inventory receipt
- Lot size / order multiple — the quantity rules that govern how much to order
- Planning method — whether an item uses MRP, reorder point, min/max, or manual planning
Every suggestion your ERP generates — every purchase order recommendation, every production order trigger, every exception flag — is the output of these parameters applied to current inventory levels. If the parameters are wrong, every output is wrong.
How Parameters Drift
Planning parameters don't go bad all at once. They drift gradually as the business changes and nobody updates the system to reflect those changes.
Demand changes, ROPs don't
A customer doubles their order frequency. Or a product gets discontinued and demand drops 60%. The reorder point was calculated based on last year's demand rate. The system doesn't know demand changed — it triggers orders based on the old rate. You either run out more than you should, or you carry inventory you no longer need.
Lead times change, safety stock doesn't
A supplier starts delivering in 45 days instead of 21. Your safety stock was calculated assuming 21-day lead times. The buffer that used to cover you no longer does. Stockouts appear on items that were supposedly protected.
Costs change, ABC classifications don't
A commodity input doubles in price. The item that was a B-class based on last year's cost is now consuming A-class budget. But the system still treats it as a B — less frequent review, lower safety stock, less planner attention. You're under-protecting a high-value item.
The Symptoms of Stale Parameters
Planning parameter drift is almost invisible until it's not. The symptoms that surface are usually attributed to something else:
- Stockouts on items the system said were covered — attributed to demand spikes
- Excess inventory building on slow-moving items — attributed to over-ordering
- Planners manually overriding system suggestions — attributed to system limitations
- Increasing expediting costs — attributed to supplier problems
In each case, the actual root cause is a planning parameter that no longer reflects how the business operates.
Why It Doesn't Get Fixed
Parameter drift is a slow, quiet problem that competes for attention with loud, urgent problems. When you're expediting an order to avoid a line shutdown, nobody is reviewing reorder points. Over time, the firefighting consumes the capacity that would have been spent preventing the fires.
There's also an institutional knowledge problem. The people who configured the parameters during ERP go-live may have left. The current team doesn't know why the parameters are set the way they are — and without documentation, changing them feels risky. So nobody does.
The Fix Is Simpler Than You Think
Fixing stale planning parameters doesn't require a new ERP or a large consulting engagement. It requires: 12-24 months of demand history, current lead times from suppliers, current unit costs, a structured methodology to recalculate each parameter by item class, and a documented process to keep them current going forward.
The recalculation work typically takes 2-4 weeks for a portfolio of 200-500 active SKUs. The resulting improvement — fewer stockouts, reduced excess, planners who trust the system again — is measurable within one to two order cycles.
Where to Start
Pull your top 20 items by annual dollar spend. Find when the reorder point was last updated for each one. Compare the lead time in your system to the actual lead time from your supplier. Check whether any of those items have an ABC or XYZ classification set. If the answers reveal parameters that haven't been touched in more than a year — you have a planning parameter problem worth addressing.