SAP Clean Core

Sometime around 2018 SAP finally realized that migrating from classing ECC to S/4 is not that easy for a customer. ECC systems are usually heavily customized, bloated with custom code, flooded with numerous background jobs - not clear what data they process and wired in with many interfaces that it is not possible to track what data they bring in/out.

Back then the SAP’s introduced a clean core strategy (remembers TechEd slogan – Keep the core clean). It is a modernization approach designed to keep the ERP system (especially SAP S/4HANA) as close to standard as possible. That means minimizing invasive customizations and technical debt. It aims to make systems upgrade-safe, cloud-ready, and innovation-friendly by shifting custom logic and extensions outside the core, typically to SAP Business Technology Platform (BTP).

Clean core principles:

·        Standardization of Business Processes – Adopt SAP Best Practices to reduce complexity.

·        Decoupled Extensions – Move custom logic outside the ERP core using BTP.

·        Integration via APIs – Ensure reliable, upgrade-safe connectivity.

·        Data Governance – Maintain clean, consistent data for analytics and compliance.

·        Efficient Operations – Reduce maintenance costs and security risks.

However, what SAP really wanted back then was to a kind of "cloud mandate" to their customers. For years there has been a pushback of that. Still many customers prefer to stay on-premise for various reasons. It makes no sense to dig to those reasons here now but surveys by ASUG/DSAG confirmed it many times. S/4 adoption did not go a pace SAP wanted it.

Now we are in 2025 when SAP comes with the lates iteration of the clean core strategy – document Clean core extensibility for SAP S/4HANA Cloud. To simply put it - they came from cloud mandate to practical reality the customers live in. Seems SAP finally gets the customers issues and they do not demonizing a custom development rather they address it more pragmatic and customer friendly approach. Within the latest strategy SAP introduces A–D extensibility model replacing old tiers for compliance and upgrade safety. Finally, a classic ABAP APIs and ABAP technologies (e.g. customer exits, SAP Script, Smart Forms, classic workflow, web dynpro ABAP) are classified as clean core compliant at level B which means are upgrade-stable.

 

Level A: Fully Compliant Extensions done with SAP Build by using only publicly released, stable interfaces backed by formal stability contracts.

·        Side-by-Side: Develop on SAP BTP using pro-code and low-code tools for applications and process automation.

·        On-Stack: Build within SAP Cloud ERP Private using the ABAP Cloud model and approved APIs.

 

Level B: Classic API-Based Extensions - Utilize SAP’s classic APIs and technologies with well-defined, documented, and generally upgrade-stable interfaces.

 

Level C: Partially Compliant Extensions - Depend on SAP internal objects for flexibility in legacy scenarios. SAP provides object change logs to help identify incompatible changes early and plan upgrades proactively.

 

Level D: Not recommended extensions not considered “clean” that use explicitly non-recommended objects or techniques (e.g., objects marked as “noAPI” in the Cloudification Repository, modifications to SAP objects, direct write access to SAP tables, or

implicit enhancements). These represent the highest risk and create significant technical

debt.

 

Level D: Non-Compliant Extensions (Not recommended/considered as clean core because it is the upgrade risk/technical debt.) - Use non-recommended objects or techniques such as:

·        Objects marked “noAPI” in the Cloudification Repository

·        Modifications to SAP objects

·        Direct table writes or implicit enhancements

 

More information:

Clean core extensibility for SAP S/4HANA Cloud

3578329 - Frameworks, Technologies and Development Patterns in Context of Clean Core Extensibility

Cloudification Repository Viewer – BW classic components listed here, none of BW artefacts has a successor in fact, but they won’t be missed as in modern BW (e.g. BW4/HANA, SAP Datasphere and BDC) replaces those old technologies completely.