As SAP users work to manage their ERP landscapes, building and extending systems in a standard, upgrade-stable way is a critical step toward reducing complexity and cost while enabling truly strategic, business-specific differentiation.
Over time, these ERP landscapes can become burdened by custom code, undocumented changes, and difficult-to-maintain integrations. Customization might solve immediate needs, but it carries hidden lifecycle costs, requiring ongoing upkeep while slowing down upgrades and introducing security risks.
SAP’s clean core approach emphasizes the use of standard processes, helping customers to build and extend SAP S/4HANA Cloud systems in a way that’s stable, agile, and upgrade-ready. (This approach is applicable to SAP S/4HANA Cloud, private edition, as the public cloud edition cannot be customized in its source code, only extended.) For SAP customers moving from on-premises systems to the cloud, building resilient business processes is a particularly important step toward accelerating innovation cycles, minimizing technical debt, and simplifying system maintenance and upgrades.
To extend SAP S/4HANA Cloud, SAP’s clean extensibility framework advises two models: side-by-side extensibility on SAP Business Technology Platform (BTP), creating scalable and decoupled applications that run outside of the core; and on-stack extensibility with ABAP Cloud, creating tightly integrated, upgrade-stable extensions within the ERP system.
Inside the Clean Core Level Concept
As SAP users seek to manage custom code in SAP S/4HANA, SAP has recently evolved its previous three-tier model for helping customers decide how to implement extensions into a “clean core level concept.” Categorizing extensions based on quality and upgrade stability, this evolved framework—with rules for classic ABAP—can guide SAP customers in prioritizing remediation of high-risk extensions and support gradual adoption of clean, upgrade-stable practices.
Described by SAP as an “enhanced maturity model,” this model for clarifying extensibility decisions and simplifying qualification criteria categorizes extensions into four levels of compliance (A, B, C, and D), based on their upgrade safety, architectural integrity, and alignment with clean core principles:
- Level A: Fully compliant extensions. Either built side-by-side on SAP BTP, using pro-code and low-code tools, or on-stack within SAP S/4HANA Cloud using the ABAP Cloud development model with publicly released APIs (available via the SAP API Hub).
- Level B: Compliant extensions. Use SAP’s classic APIs and technologies.
- Level C: Partially compliant extensions. Allow access to SAP internal objects, offering more flexibility for legacy scenarios. SAP plans to provide a changelog for SAP objects to help identify changes early and strategize upgrades effectively.
- Level D: Not recommended extensions. Use explicitly non-recommended objects or techniques, such as non-recommended objects (like those marked as noAPI in the Cloudification Repository), modifications, direct write access to SAP tables, or implicit enhancements.
How to Extend SAP S/4HANA the Right Way
Providing customers with a more detailed, granular framework to evaluate extensions on their quality and upgrade stability while supporting a more pragmatic approach to clean extensibility, this clean core level concept is intended to make it more attainable for those running SAP S/4HANA Cloud, private edition, to extend without compromising their system integrity. Those extensions categorized as Level D, for instance, should be prioritized for immediate remediation by on-premises customers moving to the cloud, as they represent the most significant technical debt and could threaten system stability.
Level D extensions are not clean core, whereas Level C extensions could be considered “conditional clean core,” in that they could become impactful during future upgrades but, as internal SAP objects, can still be managed in the interim with the right governance and documentation. Evolving SAP’s previous three-tier model, this clean core level concept provides enhanced clarification around specific risks associated with custom code, can guide developers in assessing which practices and technologies to adopt, and helps them to prioritize the highest-risk extensions.
With clean core a core component of SAP’s strategy for moving on-premises customers to the cloud, the level concept provides a framework to support the expanding suite of tools and services SAP is providing to drive customers’ success in this area. Within the RISE with SAP methodology, assets such as quality gates, the clean core success plan, and guided onboarding are intended to further assist customers in adopting clean extensibility practices.
SAP best practice is to encourage all extensions be created via SAP Build, which ensures they are optimized for SAP software development and improves interoperability with SAP S/4HANA. As part of SAP Build, Joule can also support extensibility best practices with process automation and low-code application development.
For more insights, SAP has released a white paper on clean core extensibility for SAP S/4HANA Cloud, as well as an eBook on extending SAP S/4HANA with SAP Build; SAP’s ABAP Extensibility Guide also provides context on ABAP-based extensibility for clean core, and SAP has released a free, two-hour learning journey similarly focused on the concept and aimed at beginners. An SAP note on this announcement is available here.