Lesson 3 of 5
Consumption
9 min
Listen to this lesson
Consumption is how a sales order and a forecast avoid counting the same alternator twice. When Great Lakes Fleet Services orders 120 alternators for delivery in October, and the October PIR is 400, the order consumes 120 of the 400. MRP then plans 400 in total (120 for the order, 280 still open on the PIR), not 520.
| Before the order | After an order for 120 in October | |
|---|---|---|
| October PIR (planned) | 400 | 400 |
| October PIR (open, unconsumed) | 400 | 280 |
| Sales order requirement | 0 | 120 |
| Total requirement MRP plans | 400 | 400 (120 + 280) |
Consumption mode and periods
Orders rarely land exactly on the PIR date. The consumption mode decides in which direction on the time axis an order looks for PIRs to consume, and the consumption periods limit how far it looks. SAP Learning lists the modes:
| Mode | Direction | Needs |
|---|---|---|
| 1 | Backward: consume PIRs dated before the order's requirement date | Backward consumption period |
| 2 | Backward first, then forward | Backward and forward periods |
| 3 | Forward: consume PIRs dated after the requirement date | Forward consumption period |
| 4 | Forward first, then backward | Forward and backward periods |
Consumption modes. Settings come from the product master (MRP 3) or the MRP group; the strategy group wins if both exist.
Two defaults are worth remembering. If no consumption values are maintained at all, SAP Learning states that the system uses backward consumption over 999 days. And with mode 1 but no backward interval, only requirements of the same day are consumed. Periods are counted in workdays of the factory calendar, so 30 periods can be more than 30 calendar days.
- 1 OctPIR 400Monthly bucket for October
- 10 OctOrder A: 120Mode 1 with 20 workdays backward: consumes 120 from the 1 Oct PIR
- 28 OctOrder B: 300Consumes the remaining 280 of October; 20 pieces left over
- 3 NovPIR 400Monthly bucket for November
- Next MRP runOverflowThe unconsumed 20 is planned as additional demand under strategy 40
Timing traps
- Consumption happens when the sales order is created or changed. A PIR created after the order is not consumed by it, which produces double counting. Load PIRs before orders in tests and in cutover.
- Monthly buckets and backward consumption. An order early in the month can find no PIR behind it if the period is short and the PIR sits on the first workday. Weekly PIRs or mode 2 often fit better.
- Unconsumed PIRs in the past remain demand until reorganized; they keep MRP producing for a month that is over.
- Strategy 10 is different. Orders are not planning-relevant; reduction happens at goods issue, oldest PIR first, and the forward consumption period still matters.
Choosing the settings is a business decision, not a technical one. Backward consumption suits a forecast the business trusts: orders eat up demand that was already planned. Forward consumption lets an early order use next month's forecast, which helps when customers order ahead of the plan. Contoso's planners chose backward consumption (mode 1) with 20 workdays for the alternator, after reviewing six months of order patterns with Maria, and agreed to revisit mode 2 after go-live. Write the reason into the design document; testers need it to build expected results.
What would you do?
After cutover, Luis's team loads open sales orders on Saturday and forecast PIRs on Sunday. On Monday, MRP plans almost twice the usual alternator volume. What happened?
- Consumption stops forecast and orders from being counted twice; the total stays the same.
- Mode 1 backward, 3 forward, 2 and 4 combined; periods are in workdays.
- No values maintained means backward consumption over 999 days.
- Consumption runs at sales order creation or change: load PIRs before orders.
Check your understanding · not graded
Lesson check
1. PIR 400 in October; a sales order for 120 in October consumes it. What total does MRP plan for October?
2. Which consumption mode looks only at PIRs dated before the order requirement date?
3. What happens if no consumption values are maintained anywhere?
4. Why load PIRs before open sales orders at cutover?