S/4HANA Migration: Greenfield, Brownfield, or Carve-Out?

For many companies, migrating to SAP S/4HANA is no longer a question of “if” but “how.” SAP has clearly communicated the end of maintenance for ECC, and decision-makers now need to determine which migration path is right for their organization.

The answer is rarely straightforward. Three established approaches are available — Greenfield, Brownfield, and Carve-out — and each comes with its own strengths, risks, and prerequisites. In this article, we examine all three strategies based on our experience from real migration projects.

Greenfield: The New Implementation

With the Greenfield approach, a completely new S/4HANA system is set up. All business processes are designed, configured, and implemented from scratch. Historical data is selectively migrated — only what is actually needed.

This approach offers the greatest design freedom. Companies can radically simplify processes, adopt SAP Best Practices, and leave behind years of accumulated complexity. Greenfield is often the better path, especially for organizations with highly fragmented system landscapes, numerous custom developments, or outdated processes.

Brownfield: The System Conversion

The Brownfield approach — also known as System Conversion — converts the existing ECC system in-place into an S/4HANA system. All existing data, customizing settings, custom developments, and authorization concepts are fundamentally preserved.

SAP provides the Software Update Manager (SUM) with the Database Migration Option (DMO) tool for this purpose. The technical process includes Unicode conversion, database migration to SAP HANA, and the actual S/4HANA conversion.

This path is particularly suited for companies whose existing processes are largely working well and who are not seeking a fundamental redesign. Investments in existing customizing are protected, and users can continue working within familiar structures.

Carve-out: Die Selective Data Transition

The Carve-out approach — also called Selective Data Transition (SDT) — combines elements of both previous strategies. Specific parts of an existing system are selectively extracted and transferred into a new S/4HANA system. Processes can be selectively adopted, adapted, or redesigned.

This approach is particularly relevant for corporate divestitures, mergers, portfolio cleanups, or group restructurings. A typical scenario: A corporation sells a division and needs to cleanly separate its SAP data and processes from the group system.

Tools such as SAP Landscape Transformation (SLT) and SNP CrystalBridge support selective data migration. The challenge lies in correctly delineating the data to be migrated — especially in highly interconnected organizational structures with cross-client processes.

Our Recommendation

There is no universally better migration approach. The decision depends on a variety of factors: the current system state, the available budget, the desired timeline, the complexity of custom developments, and the strategic business objectives.

In practice, we often see hybrid approaches: A Brownfield conversion as the technical foundation, combined with targeted process redesign in selected areas. Or a Greenfield project where historical data is selectively migrated from the legacy system.

What matters most is a thorough analysis phase before the project begins. In a structured assessment, we evaluate the system state together with the customer, identify critical custom developments, and define the target architecture. Only on this basis do we make a recommendation for the migration path.

Regardless of the chosen approach: An S/4HANA migration is not a purely IT project. It is a strategic transformation that must involve executive management, business departments, and IT equally. Only then can a system emerge that is not only technically modern but also optimally supports business processes.