There are three routes off ECC. None of them is best. One of them is yours.
Route selection is where S/4HANA programs are quietly won or lost — usually before anyone notices a decision was being made. Each route has a vocal camp, each camp is right about something, and none of their arguments matter until they are held against your estate, your data and your appetite for change.
The route is not a technical preference. It is a statement about how much of the past the business wants to carry forward.
Brownfield preserves, greenfield resets, selective negotiates. Choose by destination, not by departure point.
The three routes, honestly
Brownfield — convert what runs
A system conversion: the existing ECC system, its history and its processes move to S/4HANA substantially as they are. Fastest route to a supported platform, lowest process disruption — and every compromise in the current system arrives with you.
It fits when the processes genuinely serve the business, history must stay queryable in place, and the organization has little appetite — or need — for process change right now.
Greenfield — implement fresh
A new implementation against standard processes, with data migrated selectively into it. The once-in-a-generation chance to shed accumulated customization — paid for in process change, enablement effort and a longer road.
It fits when the current system embodies more workaround than design, when clean core is a genuine goal rather than a slogan, or when the operating model itself is changing anyway.
Selective — carry what earns its place
The negotiated middle: a new system, with chosen slices of configuration, code and history transitioned into it using specialized tooling. Attractive precisely because it refuses both extremes — and demanding, because every “keep or leave” call must actually be made.
It fits large, uneven estates where some regions or process areas deserve a reset and others genuinely do not — and where the organization can staff the decision-making the route exists to enable.
The four things that actually decide it
- History. Who needs the past, at what grain, and must it live in the new system — or is an archive with good access enough? This single answer eliminates a route more often than any other.
- Custom code. How much of it still earns its keep? A conversion carries it; a fresh start strands it; selective makes you decide object by object.
- Downtime tolerance. What can the business actually absorb at cutover — a weekend, a week, or phased waves? Routes differ sharply in what they ask here.
- Appetite for process change. Not the appetite stated in the steering committee — the appetite that survives contact with the first redesigned approval flow.
The mistake that outranks all three routes
Worse than any wrong route is the unexamined one — usually a conversion chosen by default, because it resembles an upgrade and demands the fewest meetings. Six months in, the program discovers it has faithfully preserved everything the business had hoped to leave behind.
The inverse failure exists too: a greenfield chosen for its purity, run by an organization with no real appetite for the process change it requires. The route must match the organization that will actually walk it — not the one on the slide.
VISCAP perspective
Route selection is a business decision wearing technical clothes. Decide it with the people who own the processes, not only the platform.
The useful assessment is short and concrete: an inventory of what runs, what is used, what is customized and who needs which history — held against the four factors above. Done early, it turns route selection from a philosophical debate into an elimination exercise. Most organizations discover the field narrows to one candidate faster than expected.
Choose the destination first
Every route reaches S/4HANA. They differ in what arrives with you. Describe the operating model you want on the other side — then pick the route that delivers that, and nothing else.