Is brownfield always faster than greenfield?

Usually in elapsed time, but not always in total effort. A brownfield conversion of a heavily customised landscape with poor data quality can exceed a clean greenfield build once remediation and testing are counted.

What happens if we miss the 2027 date?

SAP offers extended maintenance to 2030 at additional cost, and beyond that customer-specific arrangements. The practical risks are commercial rather than immediate: rising support costs, shrinking skills availability, and vendors ending ECC support for adjacent products.

When should custom code analysis start?

Before the business case is finalised. Custom code volume is the largest driver of estimate variance, and the results frequently change the recommended migration path.

SAP

S/4HANA Migration: Getting Ahead of the 2027 Deadline

By AX3 · August 31, 2026

Mainstream maintenance for SAP ECC ends in 2027, with extended options running to 2030 at a premium. For most enterprises the remaining calendar is shorter than it looks: a multi-entity global rollout consumes eighteen to thirty months, and qualified S/4HANA capacity gets scarcer every quarter. The decisions made in the next two planning cycles will determine whether this becomes a transformation or a fire drill.

Choose the conversion path deliberately

There are three credible paths, and the choice is a business decision disguised as a technical one.

Brownfield (system conversion) carries your existing configuration, history and customisations forward. It is the fastest route to a supported platform and the least disruptive to operations, but it also carries forward twenty years of process debt. Choose it when the current process model is genuinely fit for purpose and the driver is platform risk.

Greenfield (new implementation) rebuilds on standard processes. It delivers the cleanest target state and the strongest case for automation and analytics, but it is a full change program with data migration, retraining and parallel run. Choose it when the process estate is fragmented or when several legacy instances are being consolidated.

Selective data transition takes specific entities, company codes or data ranges into a new build. It is the pragmatic middle path for large groups with uneven readiness, and increasingly the most common answer — at the cost of a more complex cutover design.

Sequence around the constraints that actually bind

Three constraints tend to set the critical path: custom code remediation, integration surface, and data quality. Run the readiness check and the custom code analysis early — before the business case is locked — because the volume of incompatible objects is the single largest source of estimate error. Expect a meaningful share of custom objects to be obsolete; retiring them is usually cheaper than remediating them, but retirement requires business sign-off, which takes time.

The integration inventory is the second trap. Point-to-point interfaces accumulated over two decades rarely have current owners. Catalogue them, classify by criticality, and decide which move to modern APIs or an integration layer as part of the program rather than after it.

Treat data migration as a program, not a workstream

Master data cleansing has a longer lead time than any technical task and cannot be compressed at the end. Start profiling material, customer, vendor and finance master data in the first month, assign business data owners with named accountability, and set entry criteria for each mock conversion. Four mock runs is a reasonable planning assumption for a large landscape; teams that plan two usually discover why during hypercare.

Build the case on operating outcomes

A migration justified purely on maintenance expiry struggles for funding against commercial priorities. The stronger cases attach the move to outcomes the business already wants: faster financial close, embedded planning, real-time inventory and margin visibility, automation of manual reconciliation, and the retirement of bolt-on systems whose function is now standard. Quantify these with the process owners and track them post go-live, otherwise the program is judged only on disruption.

Protect the run while you change the platform

Every hour of ERP downtime is production, shipping and cash. Downtime-optimised conversion techniques, near-zero-downtime approaches and rehearsed cutover plans exist precisely for this. Rehearse the full cutover at least twice under production-like conditions, including the fallback decision point and who is authorised to invoke it.

Resourcing deserves the same realism. Blended teams — core client knowledge, specialist S/4HANA capability, and a dedicated remote delivery pod for testing, data and custom code work — hold schedules better than a single large onsite team, and cost materially less over a two-year program.

Frequently asked questions

Is brownfield always faster than greenfield?: Usually in elapsed time, but not always in total effort. A brownfield conversion of a heavily customised landscape with poor data quality can exceed a clean greenfield build once remediation and testing are counted.
What happens if we miss the 2027 date?: SAP offers extended maintenance to 2030 at additional cost, and beyond that customer-specific arrangements. The practical risks are commercial rather than immediate: rising support costs, shrinking skills availability, and vendors ending ECC support for adjacent products.
When should custom code analysis start?: Before the business case is finalised. Custom code volume is the largest driver of estimate variance, and the results frequently change the recommended migration path.

AX3 helps enterprises with SAP — get in touch at support@ax3global.com