If Clean Core were a TV series, it would be well into its third season by now – past the initial hype, but still evolving with new plot twists. (And if it were a Netflix series, it would have already been canceled on a cliffhanger. Ba dum tss!)
What is the latest news, and what is the practical impact for SAP customers?
Previously on “Clean Core”
The early confusion (“Are we supposed to just use plain vanilla SAP?”) has largely settled. The current direction is clearer: extend SAP systems in ways that preserve the integrity of “the core,” whether through on-stack or side-by-side approaches.
Last year, SAP also introduced Project Kernseife, helping customers assess how “clean” their systems really are – addressing a long-standing question.
The initial guidance involving a three-tier system with “wrappers” was rather confusing and impractical. Thankfully, it has been replaced with clearer and more realistic guidelines using four levels (A–D).
The Levels
SAP Note 3578329 is the ultimate source of information about Clean Core levels and their meaning. It provides a clear classification of development objects, frameworks, and patterns with regard to cloud readiness and upgrade stability. Level A is the best (cloud-ready), and Level D is the worst (“dirty”).
One notable takeaway for SAP customers is that some traditionally criticized techniques are not as problematic as commonly assumed. For example, the famous SD user exits (MV45AFZ… and similar) and VOFM routines are classified as Level B. SAPscript? Also B, along with Smart Forms. BDC (Batch Data Input)? Level C.
Level D is primarily reserved for explicit and implicit enhancements (with the exception of BAdIs) and obscure UI techniques. Overall, this new classification aligns better with realities in the SAP customer landscapes and is a welcome change.
Where Do We Go From Here?
The SAP Notes and guides provide much-needed clarity and specificity. But Clean Core, being more of a direction, not a destination, means there isn’t a single cookbook that works for every SAP customer.
The main reason is that the technology stack between S/4HANA Public Cloud and all other editions is quite different. While it is possible to use the ABAP Cloud programming model and ensure cloud compatibility even in non-Public Cloud systems, 100% adherence may not be technically feasible without sacrificing a lot of useful functionality that could still be used for years.
Ultimately, decisions about what code is worth refactoring, moving elsewhere, or leaving alone rest with the customers. If your company has no near-term plans to move to Public Cloud, you might want to prioritize projects that provide immediate business value (such as automation). However, if such projects are also impacted by some of the legacy “dirtiness,” it would be sensible to pursue changes sooner rather than later.
Final Thoughts
While “an ounce of prevention” is generally good advice, the concept of “premature optimization” also applies in software development – and it’s not a good thing. Good engineering judgment is essential and timing matters a lot in IT work.
Most importantly: let your own strategy and business priorities – not some made-up dogma or LinkedIn hot takes – guide your Clean Core initiatives.
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