A customer commitment can look safe in ATP and still be vulnerable in execution. You may have the right confirmation, the right date and the right priority, but if the supply is not fixed to that demand, another delivery can still consume it first.
That is why smart ATP algorithms are only part of the answer. They help the system check, sort and prioritize demand. But when supply is constrained, the business sometimes needs to go beyond standard prioritization: make a deliberate exception or apply company-specific distribution logic. And once that decision is made, it must survive later ATP runs, manual deliveries and operational changes. Supply Assignment, known as ARun, gives S/4HANA that decision layer. Fashion logistics has used it for decades. Outside fashion, many companies still do not know that this capability is already in the standard toolbox.
Picture a commitment you have almost certainly made at some point. A key customer needs goods from a shipment arriving next month. You agree: those pieces are yours. The system confirms the order against the incoming purchase order, the dates look right, everyone moves on.
Three weeks later, a different order, created later and arguably less important, goes to delivery first. The warehouse picks. Your customer’s confirmation quietly recalculates to a later date. No error message, no alert, no fingerprints.
Nothing malfunctioned. Another user simply had access to manual delivery creation and overruled the confirmation without knowing it. The system had no way of telling that your agreement with the customer was already fixed. A confirmation is a ranking, not a reservation: flexible by design, and by itself it does not put your customer’s name on specific goods.
The classic remedies are well known, and they work: restrict who may create deliveries manually, or, for fixed customer agreements, create the deliveries early, even before they are final, and wait for the customer’s green light. But where customers control the timing and scope of their deliveries, that second path has a price.
I have seen the price. Two disciplined, mature companies, not improvising startups, used to create and delete thousands of outbound deliveries every night: a batch job whose only purpose was to hold reservations that had nowhere else to live. They ran that carousel for years. When a workaround grows that heavy, it stops being a workaround. It becomes infrastructure nobody dares to touch.
Real life is full of exceptions
Anyone who has brought a special requirement into an ATP discussion knows the pattern: check logic, sorting rules, exceptions and restrictions around the exceptions. All of that exists for good reason, because an automatic check can only keep its promises if everyone plays by the same rules. And yet the conversation somehow always ends with what the system will not let you do.
Meanwhile, real life keeps producing cases the rulebook never covers: a contract that must jump the queue, a market that must get its share in a shortage, a shipment that belongs to one customer, full stop. In those moments, the point is not to reject automation. The point is to complement it. The business needs a controlled way to make a decision, fix it in the system and know that later checks, deliveries and warehouse movements will respect it. That right exists. One industry has simply had it for decades.
A fashion secret, now in the standard toolbox
That industry is fashion. Supply there is seasonal, scarce and non-repeatable. If the goods meant for a key account’s spring launch get consumed by someone else, there is no second production run to fix it. So SAP’s fashion solutions have long carried a dedicated instrument for exactly this: the allocation run, or ARun. Ask anyone who grew up in SAP fashion logistics and they treat it as a given; many would be surprised to learn the rest of the SAP world ever lived without it.
With S/4HANA, that changed. The capability now lives in the advanced ATP family as Supply Assignment (ARun), available to every industry, not only fashion. But because it spent its life inside a niche vertical, knowledge outside fashion is thin. And here lies a trap: when an S/4HANA transformation starts, business teams naturally anchor to what they know from ECC. Decades of workarounds feel like best practice. The functions you have never heard of are precisely the ones that never make it into your design, and this one deserves to.
And notice what kind of tool it is. Supply Assignment is not the opposite of ATP. It sits beside the algorithms, not against them. Automated checks keep protecting the common case. Supply Assignment gives the business a governed decision layer for the cases that must not drift after the promise is made: freedom with rules, statuses and a clear trace, rather than improvisation. Nothing is taken away, and the business gains levers it did not have before, especially where requirements go beyond a sequential, one-order-after-another distribution of supply.
The core idea: pin demand to supply
Supply Assignment does one conceptually simple thing. It pins a specific demand, such as a sales order item or a stock transfer to your own store, to a specific supply: a purchase order, an inbound delivery, a production order, a batch or stock on the shelf.
While that pin holds, the supply is untouchable. Other orders cannot confirm against it. A delivery for someone else cannot consume it. If you choose, even warehouse movements such as scrapping can be blocked. The link can be set months in advance, by hand for the exceptions or, most commonly, automatically in mass runs driven by the same prioritization engine that already re-checks your order book overnight. It slots into the operational rhythm you have today.
And the pin is not a life sentence. Every assignment carries a status, and statuses behave differently by design: some the nightly run is allowed to release and re-optimize, others lock the link finally, immune to any later run. So the business should not picture assignment as something static. It is a controlled lifecycle, and the business decides how firm each pin is, per situation.
A confirmation ranks supply. An assignment fixes a business decision to specific goods.
Seven things this changes
If you already know ARun
A note for my fashion readers, the ones tempted to skip the S/4HANA chapter as a re-run of a familiar story: don’t. The tool has outgrown its origins. Cross-docking on assignments (04) simply wasn’t possible in the AFS world. The way custom, company-specific distribution logic can now be built on the standard core (05) opens doors that used to demand heavy workarounds. And the traceability story (07) was never on the table. Even the two delivery-carousel companies from the beginning of this article ran their nightly job on AFS, with the classic ARun already in the house. What forced them into that workaround then is handled far more elegantly by the S/4HANA version. Moving to S/4HANA doesn’t just preserve what you had. Even the veterans get new toys.
Who should take a look
If demand regularly exceeds supply; if you make customer-specific commitments; if you run your own store network; if parts of your logistics are outsourced, this deserves a place on your S/4HANA shortlist. That describes far more than fashion: consumer brands, pharma, components and hi-tech distribution live with exactly these patterns. And the best moment to look is before your availability design is locked, not after go-live, when the old workarounds have already been faithfully rebuilt.
These seven are only the most visible uses. There are more, especially in combination with the rest of the advanced ATP toolbox. Functions like this one are, to me, the quiet argument for S/4HANA: capabilities that industry pioneers once paid dearly to build are now sitting in the standard toolbox, waiting to be noticed.
And if this article made something click, there is a logical next step that doesn’t require calling anyone yet: a preliminary discovery with your own team. SAP’s official training chapter on the topic, Explaining Supply Assignment, covers the machinery in full depth. Fair warning: it is genuinely technical, written for consultants rather than business readers. But that is exactly the right division of labor: you bring the scenario and the ambition; let your team verify the mechanics.
Try it on before you buy it
In fashion, nobody commits without a fitting room. We built one for ATP: the SizeGrid ATP Vision Lab, a live, preconfigured S/4HANA environment where scenarios like these run as working prototypes, not slides. Bring your scenario; see it on screen within days.
If any of the seven made you think “that’s us”, discuss your ATP landscape with us.
And one question to the logistics leaders reading this: how often do manual deliveries overrule your carefully tuned confirmations, and would your system even show it? I’d genuinely like to hear how different companies live with this. Join the discussion on LinkedIn or get in touch.
Andriy has worked with ARun and Supply Assignment for more than a decade, from its origins in SAP AFS through FMS to S/4HANA advanced ATP. At SizeGrid he leads the design of advanced ATP concepts, fair distribution mechanisms and SAP extensions for constrained-supply scenarios.