The clean-core strategy for SAP S/4HANA is designed to maintain the integrity and upgradeability of the digital core. This is achieved by ensuring that all extensions and customizations are built in a decoupled manner. The fundamental principle is that extensions must exclusively use stable, released, and supported public APIs and extension points. This approach guarantees that when the core SAP system is upgraded, the custom extensions continue to function without requiring rework. Conversely, changes to extensions do not impact the stability of the core system. This mutual protection ensures operational stability, reduces total cost of ownership (TCO), and facilitates faster innovation cycles.

B: This is incorrect because the clean-core principle explicitly forbids direct access to SAP tables. Such access creates tight coupling and is a primary cause of failures during system upgrades.

C: This statement is too absolute and therefore incorrect. While side-by-side extensibility is a key part of the strategy, on-stack (in-app) extensibility is also a valid and often necessary approach within a clean core, provided it uses released APIs.

1. SAP White Paper: Guiding Principles for a Clean Core with SAP S/4HANA. This document states

"A clean core means that the SAP S/4HANA system is kept as close to the standard as possible... Customizations are implemented in an upgrade-stable way

primarily through the use of released SAP APIs." It explicitly advises against modifications of SAP code and direct access to SAP database tables.

2. SAP Help Portal: Extensibility Guide for SAP S/4HANA Cloud. The guide emphasizes

"To keep the core clean

you can only use released SAP objects (APIs

CDS views

and so on) for your extensions. This ensures that your extensions are upgrade-stable." (Section: Extensibility Concept).

3. SAP Application Extension Methodology: This methodology provides a decision framework for choosing the right extension tool. It does not state that side-by-side is "always" preferable but guides architects to choose between on-stack and side-by-side options based on specific technical and business requirements

thus refuting the absolute claim in option C.