7 Things to Consider Before an SAP S/4HANA Migration

Most of what makes or breaks an SAP S/4HANA migration has little to do with the tech. It comes down to seven calls: do you have a real business case, which path fits (greenfield, brownfield, or selective), how clean is your data, what shape is your custom code in, where will it run, and can you fund the timeline you actually need? Sort those out and go-live is quiet. Skip them and every old problem tags along for the ride.

Nobody migrates to SAP S/4HANA over a long weekend. This is a bet on how your business runs for the next decade, and it has a habit of punishing anyone who treats it as a pure IT job. The teams that come out bruised? They rarely hit a technical brick wall. They waved off the hard questions early and paid for it later, chasing scope, data problems, and cost overruns the whole way through.

And there’s a deadline breathing down everyone’s neck. SAP pulls the plug on mainstream maintenance for ECC on 31 December 2027, and the nearer that gets, the tighter and costlier the market becomes. Counterintuitive as it sounds, that’s exactly why you want to take your time at the front of the project, not the back. The seven SAP S/4HANA migration considerations that follow are the ones I’d settle before signing off on a date, a partner, or a path. Would you rather not go it alone? That’s the whole point of an AI-assisted SAP S/4HANA migration.

What is an SAP S/4HANA migration?

So what does an SAP S/4HANA migration actually involve? At its core, you’re moving off an older SAP ERP (usually SAP ECC) onto SAP’s current platform, S/4HANA, and dragging your data along with you. What sets it apart from a bog-standard upgrade is the plumbing underneath. S/4HANA runs on a leaner data model and the in-memory HANA database, which means tables you’ve leaned on for years, chunks of custom code, reports people depend on every morning, a fair bit of it has to be reworked.

Which is why an SAP ECC to S/4HANA migration is a business project first and a technical one second. You’re not nudging a version number forward. You’re making calls: which processes survive, which get torn down and rebuilt, and how much of your history is worth hauling across.

Why migrate to SAP S/4HANA now?

Waiting doesn’t save you a penny here. If anything, it adds to the bill. Three forces are tightening the screws on your timeline.

SAP ECC support ends in 2027

On 31 December 2027, SAP turns off mainstream maintenance for ECC (Business Suite 7). Sure, you can buy an extension to 2030 for a fee, and a small club of really big or really complex shops can push further still through RISE with SAP. But the day mainstream support stops, so do your security patches, your legal updates, your technical fixes. Try walking into a board meeting and proposing you run finance and supply chain on an unsupported system. See how far that gets.

The cost of waiting

Imagine every ECC customer on earth shuffling toward one exit at the same moment. That’s more or less the situation. The closer 2027 gets, the harder it is to find seasoned SAP people, and the ones you do find charge more. On top of that, the Compatibility Packs (the things that let certain old ECC functions keep running inside S/4HANA) start expiring around now, so your room to move shrinks. Get in while there’s slack and you call the shots on approach. Drag your feet and you may get boxed into a rushed conversion, because it’s the only thing that squeezes into the calendar.

What you gain

Staying supported is just the price of entry. The upside runs deeper. Instead of waiting on overnight batch jobs, you get data in real time. You get the Fiori interface. You get a Clean Core setup that keeps your next upgrade from turning into a project of its own. And AI ships in the box now, Joule and SAP Business AI both, tucked right into the work your teams do all day. In practice, most of the payback only shows up once you’re running on an AI-enabled SAP S/4HANA core.

7 key SAP S/4HANA migration considerations

Seven things to settle before anyone kicks off. Treat them as decisions you owe yourself up front, not documentation to file away. Each one tugs on your cost, your timeline, and how much you squeeze out of S/4HANA down the line.

1. Define your target state and business case

First question, and it’s a blunt one: why are you doing this at all? Running a quick proof of concept, or heading straight into production? Trying to stay supported with minimal fuss, or using the disruption to finally fix processes while the hood’s already up? Whatever the answer, write it in plain words. The migrations I’ve watched go off the rails almost always started with something woolly like “let’s implement S/4HANA” and never agreed what a win looked like. Nail the business case and, funnily enough, it more or less chooses the path for you.

2. Choose your migration path

There are three ways in. Which one suits you depends on a single question: how much of what you’ve already got is worth keeping?

Greenfield

Blank slate. You stand up S/4HANA from scratch, build your processes around SAP’s standards, and wave goodbye to the old customisation. Makes sense when your current system is long in the tooth, patched to within an inch of its life, or just doesn’t match how you work anymore. Heavier lift, but the reward’s bigger too.

Brownfield

A straight conversion. You lift your existing ECC system, its config, its history, and set it down on S/4HANA more or less intact. Faster, less upheaval. The trade-off? You’ll haul the old complexity along with you unless you tidy up en route.

Selective (Hybrid)

The middle lane, sometimes called bluefield. Keep the processes and data that pull their weight; rebuild the rest. You decide what changes and what doesn’t, though it takes sharp scoping and, usually, a third-party tool to pull it off.

3. Check your system and data readiness

Measure first. Always. The SAP Readiness Check tells you how much is going to break. The ABAP Test Cockpit puts a number on your custom code. And somebody, ideally someone without a stake in the answer, needs to give your data an honest grade. This is the step where gut feelings turn into evidence you can plan around. A proper SAP discovery and evaluation does precisely that, and pound for pound it’s the cheapest insurance on the whole job.

4. Plan data migration and cleansing

Not every record has earned a seat on the bus. Work out early what travels, what gets archived, and what you leave at the curb. And clean it before you move it, not after, because dirty data tipped into S/4HANA just recreates yesterday’s mess on a faster kit. Want the order of play spelled out? Our rundown of the core SAP S/4HANA migration steps walks you through it.

5. Sort out custom code and integrations

Clean Core rewards standard config and side-by-side extensions, and it frowns on hacking the core itself. So haul every customisation into the dock and make it justify its existence. Does it still pull its weight, or was it a workaround for something SAP now does natively? While you’re in there, map your integrations. Migrations have a nasty habit of surfacing brittle point-to-point links that need rebuilding, not just a fresh round of testing.

6. Pick your operating model and deployment

So where does S/4HANA actually live? On-premise, private cloud, public cloud, and, increasingly, inside RISE with SAP as the wrapper around all of it. Mostly standard processes? Public cloud and its rolling updates will suit you fine. Carrying heavier customisation? You’ll likely be happier on SAP S/4HANA Private Cloud, with a steadier base to build on. Already parked on a hyperscaler? The same logic behind migrating SAP to Azure applies: pick the model that matches how much control and customisation you truly need, not whichever one has the shiniest label.

7. Plan budget, timeline, resources, and change management

Budget for the stuff that hides. Data prep alone can swallow a quarter of the effort, and it belongs to your senior people, not whoever’s got a free afternoon. Set the timeline after the readiness check hands you real numbers, never before. And whatever you do, don’t bolt training on at the end. A migration that’s spotless on paper but shunned by the people meant to use it hasn’t succeeded, it’s failed. Tell folks what’s coming early, train them by role, and give them a reason to want the switch.

How does an SAP S/4HANA migration work?

SAP hands you a playbook for the whole thing, called SAP Activate. It runs in six phases:

1. Nail the business case, run the readiness check, sketch out the target architecture.
2. Stand up the environment, plan the work, get the team in a room.
3. Fit-to-standard workshops that decide what stays standard and what has to bend.
4. Build it, configure it, move the data, test in cycles.
5. Cutover, go-live, hypercare.
6. Steady the ship, then start making it better.

Discovery’s the one everyone speeds through and later kicks themselves over. It sets the tone for everything that follows.

Technical vs process-oriented implementation

Every migration breaks into two halves. The technical half, moving the database to HANA, reshaping the data model, swapping out program code, standing up Fiori, is well tooled and reasonably predictable. The other half is the messy, human one: redrawing how work flows, wiring up new processes, sorting roles, and coaxing people onto them. The upside? You can usually run the process side on its own track, apart from the technical cutover, so one never ends up holding the other hostage.

How AI is changing SAP S/4HANA migration in 2026

Rewind two years and “AI in your migration” meant a slide in the pitch deck and not much else. Not anymore. AI-assisted tooling now chews through your custom code and flags what an upgrade will snap, grades your data quality before a single record budges, and drafts test cases so QA isn’t starting from nothing. Does any of that put consultants out of a job? No. It clears the drudgery off their desks, so the experienced ones spend their hours on the judgement calls instead of grinding through analysis by hand.

And once you’ve gone live, SAP Business AI carries the same smarts into daily operations, flagging odd numbers in finance, tightening up forecasts, that sort of thing. It’s how we run delivery at Accely: AI-assisted wherever it saves time, with our people keeping a firm hand on every decision that counts.

Common SAP S/4HANA migration challenges

Most migrations stumble over the same short list. Spot them early and you’ve won half the fight.

• Dirty data. Duplicates, dead records, entries that contradict each other. It slows the move and poisons the new system. Scrub it first.
• Custom code nobody claims. Years of ABAP written by people are long gone. Get the ATC on it early, not when you’re neck-deep in testing.
• The skills crunch. As 2027 looms, decent SAP hands get scarce. Book your team well ahead.
• People digging in. New screens, new roles, new habits are a lot to ask of anyone. Bring users along early, or watch adoption stall.
• Scope creep. “While we’re in here…” is exactly how a timeline doubles when nobody’s watching. Agree the scope, then defend it.

Benefits of migrating to SAP S/4HANA

Handle it well and here’s what lands on your side of the ledger:

• Reporting in real time, not whenever last night’s batch decides to finish.
• A tidier, role-based experience courtesy of SAP Fiori.
• A Clean Core, so the next upgrade stays cheap and quick instead of turning into another epic.
• AI baked right in, Joule and SAP Business AI both, sitting inside the day-to-day.
• A lighter data footprint and fewer systems to babysit, which quietly drags your total cost of ownership down.
• Cloud headroom to scale without ripping out and rebuilding your infrastructure.

How Accely approaches your SAP S/4HANA migration

Accely’s an SAP Gold Partner with 23+ years buried in enterprise SAP and 950+ organisations served across the map. We run migrations the way this piece says to plan them: readiness first, the path picked on evidence rather than a hunch, and the data work put in senior hands. Our SAP S/4HANA data migration approach uses AI to speed up the assessment, the code remediation, and the testing, while our consultants stay on the hook for the decisions and the outcome.