SAP S/4HANA Migration in Switzerland: Greenfield, Brownfield or Selective?

Q: What is the deadline for moving to S/4HANA?

SAP mainstream maintenance for SAP ECC ends on 31 December 2027, with optional extended maintenance available until the end of 2030 at an additional cost. Swiss organizations still on ECC should be planning or executing migration now.

Swiss organizations running SAP ECC are approaching a well-known deadline: SAP mainstream maintenance for SAP ECC ends on 31 December 2027. After that, extended maintenance is available at a cost, but the strategic direction is clear. SAP S/4HANA is where SAP is investing, and everyone on ECC needs a migration plan.

This article breaks down what an S/4HANA migration actually involves, the three migration approaches, what to expect for timeline and effort in a Swiss context, and the authorization and security decisions that should be made during the project rather than after it.

The Three S/4HANA Migration Approaches

SAP documents three formal migration paths. The choice is not just technical. It determines the cost, the timeline, the amount of change management needed, and how much of your existing investment in SAP customizations you preserve or discard.

Greenfield: A Fresh Implementation

Greenfield means implementing S/4HANA as a new system, configuring it from scratch using SAP Best Practices (Activate methodology), and migrating only the master data and selected historical transactions from the existing ECC system.

When Greenfield makes sense:

Your existing SAP system has accumulated heavy customizations that no longer reflect current business processes.
You are planning a broader business transformation (new operating model, new organizational structure, M&A integration).
Your ECC implementation was never fully standardized and cleanup would cost more than a fresh start.
You want to adopt cloud deployment (Rise with SAP, Grow with SAP) and standardized best practices.

Tradeoffs: longest project duration, highest business change impact, most expensive user training, but the cleanest long-term result.

Brownfield: Technical System Conversion

Brownfield converts the existing ECC system into S/4HANA in place. The database is migrated to HANA, SAP runs a technical upgrade process, and custom code is remediated to comply with S/4HANA simplifications.

When Brownfield makes sense:

Your ECC implementation is functionally stable and reflects your current processes.
You need to preserve transaction history and avoid a data migration project.
You want to minimize business disruption and keep project cost contained.
Your custom code volume is manageable or can be modernized within the project.

Tradeoffs: you inherit your existing technical debt, including any SoD conflicts, obsolete custom code, and authorization model weaknesses. Fast to complete, but does not by itself fix underlying issues.

Selective Data Transition

Selective Data Transition is a hybrid: re-implement S/4HANA with clean configuration, then selectively migrate specific legal entities, document types, or historical periods from ECC. This approach requires specialized tooling (SAP SLO services or third-party conversion platforms).

When Selective makes sense:

Multi-entity groups where some entities are ready to transform and others are not.
Organizations carving out or divesting parts of the business during migration.
Companies with strict data retention requirements that cannot simply drop history.

Tradeoffs: most complex to plan, requires experienced migration architects, but offers the most flexibility.

S/4HANA Migration Timeline in a Swiss Context

For mid-sized Swiss organizations (CHF 50M–500M revenue, 1–5 legal entities in SAP), realistic durations are:

Approach	Typical duration	Key cost drivers
Brownfield conversion	9–18 months	Custom code volume, integration landscape, authorization cleanup scope
Greenfield (single entity)	12–18 months	Process redesign workshops, data migration, change management
Greenfield (multi-entity)	18–30 months	Rollout waves, localization (Swiss, French, German requirements), consolidation
Selective Data Transition	18–36 months	Conversion tooling, data scoping, parallel runs

A Swiss project usually needs to account for specific requirements around VAT, Swiss payroll (if HCM is in scope), local e-invoicing evolution, statutory reporting, and language considerations across the cantons. These are not S/4HANA blockers, but they drive testing effort.

Authorization Redesign: Do Not Skip This

One of the most consistent mistakes in S/4HANA migrations is treating authorizations as a post-go-live activity. This is the single best opportunity to fix the access management problems that accumulated over years of ECC use. Specifically:

Fiori apps change the access landscape. The business role concept in S/4HANA, combined with Fiori launchpad, requires a different role design than classic transaction-based ECC roles. A direct port of ECC roles into S/4HANA is technically possible but leaves significant value on the table.
SoD conflicts carry over otherwise. If your Brownfield migration brings your current roles unchanged, you bring your current Segregation of Duties conflicts with you. Our SAP SoD guide covers the common conflicts and how to detect them.
Emergency access (Firefighter) design should be defined early. S/4HANA deployments typically involve redesigned emergency access workflows, tied to SAP GRC Access Control or equivalent.
Custom authorization objects need a review. Custom authorization objects referencing ECC-only transactions will need remediation or replacement.

Treating authorization redesign as part of the migration, not a clean-up afterwards, reduces total cost and delivers a compliant system at go-live.

How MTC Delivers S/4HANA Migrations

We are a Geneva-based SAP consulting firm specialized in SAP security, authorizations, GRC and risk analysis. On S/4HANA migrations, our core contribution covers:

Pre-migration assessment: code remediation scope, authorization model diagnostic, SoD baseline (using MTC Skopos), Fiori readiness.
Migration approach recommendation: Greenfield / Brownfield / Selective decision, supported by a cost and risk comparison.
Authorization redesign: business role design, SoD-clean role catalogue, firefighter process definition, integration with identity providers.
Go-live cutover support: authorization testing, emergency access readiness, post-go-live access review.
Post-migration SoD remediation: running continuous SoD analysis on the new S/4HANA system.

For large transformation programs that require full functional SAP expertise (FI/CO, MM, SD, HCM, production planning, technical conversion), we partner with leading global audit, risk and technology consulting firms to deliver end-to-end programs. This means a Swiss-based senior team focused on your security and authorization outcomes, backed by the functional delivery capacity of a large firm when the scope requires it.

Where to Start

Before committing to an approach, most Swiss organizations benefit from a short (2–4 week) readiness assessment covering:

Custom code complexity and S/4HANA compatibility.
Current authorization model health and SoD exposure.
Integration landscape dependencies.
Data migration scope and archiving decisions.
Rough cost and duration estimates for each migration approach.

From there, you can build a business case with credible numbers rather than vendor talking points.

Based in Geneva and active across Suisse Romande, we help Swiss organizations plan and execute S/4HANA migrations with a clear view of the authorization and security decisions that matter most. Contact us to discuss your migration plans.

Frequently Asked Questions

What is SAP S/4HANA migration?

SAP S/4HANA migration is the transition from SAP ECC or a third-party ERP to SAP S/4HANA, SAP's next-generation ERP running on the HANA in-memory database. It can be done as a Greenfield (new implementation), Brownfield (system conversion) or Selective Data Transition (hybrid).

What is the deadline for moving to S/4HANA?

SAP mainstream maintenance for SAP ECC ends on 31 December 2027, with optional extended maintenance available until the end of 2030 at an additional cost. Swiss organizations still on ECC should be planning or executing migration now.

Greenfield vs Brownfield S/4HANA: which is right?

Greenfield is a full re-implementation starting from SAP best practices, best for organizations wanting to clean up legacy customizations. Brownfield is a technical conversion preserving custom code and history, faster but inherits existing technical debt. Selective Data Transition migrates specific legal entities or data scopes.

How long does an S/4HANA migration take in Switzerland?

A mid-sized Swiss organization typically needs 9 to 18 months for Brownfield conversion and 12 to 24 months for a Greenfield implementation. Complexity drivers include custom ABAP code volume, number of legal entities, integration landscape and authorization redesign scope.

Do we need to redesign SAP authorizations for S/4HANA?

Yes. S/4HANA introduces new Fiori apps, business roles and authorization objects that differ significantly from ECC. An authorization redesign during migration is the best opportunity to clean up SoD conflicts, retire unused roles and align access with actual job functions.