Analysis of clean core approaches for SAP S/4 Hana migration

With the end of support for ECC 6.0, many companies migrating to S/4 face the challenge of avoiding complex customizations. Such modifications can make future upgrades more difficult and increase costs. LeverX's clean-core strategy is about maximizing the flexibility and performance of S/4 by sticking closely to SAP's standard functionalities. This minimizes customizations that could hinder updates or prevent the introduction of new innovations. By maintaining a clean S/4 core, companies get smooth updates, faster implementations and continuous access to the latest tools and features from SAP.

How can the system be adapted to individual requirements? Three approaches to clean core extension come into play: in-app key user, on-stack developer and side-by-side extensibility on SAP BTP. The first two approaches work directly within S/4, while side-by-side extensibility uses the BTP and thus enables flexible customization via a separate platform.

In-app key user

In-app extensibility is ideal for simple customizations directly in S/4 Hana and for scenarios where business users need to make quick adjustments without extensive technical intervention. This approach supports low-code/no-code changes, such as creating custom fields, form templates or basic analytics directly within the SAP S/4 Hana environment.

The approach enables the customization of existing user interfaces, provides options for creating custom analyses, facilitates access to data and the management of templates and business objects. Non-developers are empowered to make customizations directly in S/4 Hana. This reduces the need for external integrations and enables seamless system upgrades. In-app extensibility is suitable for companies that require simple or cosmetic customizations without compromising SAP's built-in functionality.

On-stack developer

On-stack developer extensibility is optimal for advanced customizations directly in S/4 with frequent data interactions. It is essential for organizations that require deep customizations, such as adding application logic or developing new business objects that require tight integration with S/4 data. By leveraging the Abap programming language and environment, this approach enables complex customizations while keeping the changes within the S/4 environment.

It supports the addition of complex application logic and enables the creation of user-defined business objects. The approach ensures optimum data consistency by operating directly in S/4. External dependencies, e.g. through API calls, are avoided. This increases system integrity. On-stack developer extensibility is perfect for custom applications that require real-time data interactions within S/4 to ensure a consistent and responsive system as part of the classic Abap stack.

Side-by-side

Side-by-side extensibility on SAP BTP is ideal for independent applications that run outside of S/4 and leverage advanced capabilities such as AI, machine learning, IoT, data science, process automation and other powerful low-code/no-code environments to build business applications. This approach enables organizations to innovate without compromising the S/4 core and provides a stable foundation for complex cross-platform integrations. Side-by-side enables advanced enhancements such as updating user experiences, mobilizing solutions, creating cloud-native applications for B2B and B2C, and adding data science capabilities.

One of the key benefits of the approach is that the S/4 core is kept clean by running independently, reducing upgrade challenges and improving cloud readiness. Projects that require extensive customization or cross-system integrations benefit from the processing power and flexibility of SAP BTP. It is also beneficial when external users (who may not be part of S/4) need access to applications.

Choosing the right concept

The choice of an extension concept depends heavily on the individual requirements, complexity and long-term goals of a company. Each strategy within the Clean Core framework - whether in-app, on-stack or side-by-side - serves different purposes and fulfills different requirements for flexibility, scalability and system integrity. Sometimes, however, a hybrid approach can be the best solution. By evaluating each individual case, companies can determine the most suitable combination of methods to achieve their development goals.

All of these approaches have the same basic principles, which are aimed at maintaining a clean core. These include avoiding unnecessary customization, aligning with SAP standards and regularly reviewing technical debt to optimize systems. The focus is on a zero change policy, using SAP BTP for additional innovation, while relying on standard APIs and events for automation and ensuring that all enhancements are cloud-ready and adaptable to future developments. When looking at specific enhancement strategies based on customer types, two concepts are usually followed: the brownfield approach or the greenfield approach.

Brownfield

A system changeover in the sense of the brownfield approach affects companies that want to migrate from an existing SAP ERP system to S/4 while maintaining continuity and optimizing processes. A clean-core mentality removes unnecessary adjustments, creating a stable basis for enhancements and modernizations. This strategy preserves valuable legacy data and is based on SAP best practices so that companies can exploit the full potential of the system.

Greenfield

The greenfield approach is used by companies that are implementing S/4 Hana for the first time. It offers a fresh start without outdated customizations and enables an optimized, scalable setup. The new implementation facilitates the gradual introduction, simplifies future updates and ensures an optimized, scalable setup. With minimal customization, this strategy ensures that the SAP environment adheres to best practices and responds flexibly to changing requirements.

Even if a migration to S/4 is not planned in the short term, it is crucial to reduce existing technical debt. By adopting new technologies at an early stage and pursuing a clean-core approach, future development costs can be significantly reduced. This proactive strategy not only minimizes business disruption, but also ensures that the system remains agile and future-proof.

Choosing the clean-core approach is critical to building a sustainable S/4 environment. Partners like LeverX bring strategic expertise to ensure a smooth transition. In the next article, we will explore how a well thought-out strategy and the application of best practices can enable an efficient migration.

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