SyteLine MRP vs APS vs Infinite APS explained

Short answer

SyteLine can plan in three modes. MRP plans level by level through the bill of material, batches similar requirements, works backward from due dates by lead time, and ignores capacity. Infinite APS plans one demand at a time, in priority and due-date order, through its whole BOM, and schedules against shift time but assumes resources can do unlimited work during a shift. APS does the same but respects real resource availability: each resource does one task at a time. APS gives the most realistic dates, but only if your routings, resources and shifts are accurate, and it needs APS licensing and the APS services running. On customer order lines, MRP disables the availability buttons, Infinite APS shows Get ATP, and APS shows Get CTP.

The three modes side by side

	MRP	Infinite APS	APS
Plans in what order	By the lowest BOM level where each item appears, end items first	One demand at a time, by priority and due date, through its whole BOM	Same as Infinite APS
Capacity	Ignored	Limited only by shift time; unlimited tasks per resource	Real: each resource does one task at a time, on shift, when not busy
Uses routings and shifts	No	Shift time	Yes, resources and shifts
Timing	Backward from due date by lead time, batching requirements	Scheduled against on-shift time	Scheduled against resource availability
Outputs	Planned orders, exception messages	Planned orders, exceptions, resource usage	Planned orders, exceptions, resource usage
Order line button	Disabled	Get ATP	Get CTP
Licensing	Standard	Standard	Needs SyteLine APS

How APS plans a demand

APS takes one demand, such as a customer order line, and plans everything it needs down the whole BOM before moving to the next demand:

It pull-plans backward from the due date.
If a component can't be ready in time, it push-plans the whole demand forward from today and gives you a realistic, later date.
It never plans into the past.

That's the big difference from MRP. MRP tells you what you should do to hit the date, even if it's impossible. APS tells you when you can actually deliver.

Things that surprise people when they switch to APS

APS doesn't combine planned orders by default. Several small planned orders for the same item are normal. The Planned Orders Consolidation option on Planning Parameters changes this.
APS prefers a new planned order to moving an existing job. It usually creates a new, earlier planned order rather than rescheduling a job you already have. It uses existing supply within the Supply Usage Tolerance.
Frozen operations keep their allocations on later runs.
The plan is rebuilt, not edited. APS Planning deletes the existing plan and rebuilds it from current data. Most sites run it nightly, over a horizon of one to two months.
The Scheduler is separate, and usually runs over a shorter horizon, a day or two. Its changes to operation dates can move frozen operations on later runs.

Plan on Save and ATP/CTP

Plan on Save: when it's selected, a newly saved transaction, such as a customer order line, is slotted into the existing plan straight away, using unallocated capacity and supply, without waiting for the nightly regeneration.
ATP / CTP: tests one demand against a temporary copy of the plan and returns a feasible date. If the date is acceptable, you commit it. Sales should use this before promising a date, not after.

Which mode should you use?

MRP suits you when: - capacity is rarely the constraint, for example mostly purchased-and-assembled products - routings and resources aren't maintained accurately enough to trust a capacity plan - you're not licensed for APS

Infinite APS suits you when: - you want demand-by-demand planning and realistic material dates - but you don't trust your resource data enough for finite scheduling yet

APS suits you when: - capacity really is your constraint (machines, crews, fixtures) - routings, run times, resources and shifts are accurate and maintained - you're licensed and the APS services are reliably running

The honest rule: APS is only as good as your routing and resource data. Finite scheduling on inaccurate run times produces confident, wrong dates. Clean the data first, then switch modes.

When planning results look wrong

Check the services (APS modes). The APS services and planner database must be running on the SyteLine servers. If they're down, planning results are stale or missing.
Check when it last ran. A plan from last week isn't today's plan.
Trace one item by hand. Pick a planned order that looks wrong and walk back: the demand, the BOM, on-hand, open supply, lead time or routing. The cause is almost always data: a lead time, a BOM quantity, a unit of measure, or a missing routing.
Check for slow or failing runs in Background Task History. A planning run that's started failing or taking hours is worth fixing early. See Why your SyteLine report is slow for the same approach applied to heavy processes.

Switching modes

Infor documents the steps for switching between APS and MRP modes for your version. Treat a switch as a project, not a setting change: test it on a copy, compare plans side by side for a few weeks, and train planners and sales on what the new dates mean.

FAQ

What's the difference between MRP and APS in SyteLine?

MRP plans by BOM level and ignores capacity. APS plans each demand through its whole BOM in priority order and schedules against real resource availability.

Why is the Get CTP button disabled in SyteLine?

The planning mode is MRP, which disables it. Infinite APS shows Get ATP. APS shows Get CTP.

Does SyteLine APS consider machine capacity?

APS mode does: each resource handles one task at a time, on shift. Infinite APS only limits by shift time, and MRP ignores capacity.

Why does SyteLine APS create so many planned orders?

APS doesn't consolidate planned orders by default. Turn on Planned Orders Consolidation on Planning Parameters if you want them combined.