Clean Core Foundations

• QuestionWhat is "What Clean Core actually means"?Tap to revealAnswerClean Core means your extensions sit beside SAP standard on stable, released contracts — so upgrades don't break them.
• QuestionIn "What Clean Core actually means", explain:Tap to revealAnswerClean Core is a placement-and-method contract, not a ban on Z code.
• QuestionIn "What Clean Core actually means", explain:Tap to revealAnswerSix dimensions: software stack, extensibility, integrations, processes, data, operations (the Dec-2025 'five guiding principles' drop software stack).
• QuestionIn "What Clean Core actually means", explain:Tap to revealAnswerThe goal is upgrade-stability: SAP changes the core, your extensions keep working.
• QuestionIn "What Clean Core actually means", explain:Tap to revealAnswerExtensions sit beside the core through released contracts — never inside it.
• QuestionAnalogy for "What Clean Core actually means":Tap to revealAnswerBuild an extension on the official power outlet, not by splicing into the wiring inside the wall.
• QuestionWhat is "Extensibility approaches and clean-core levels (A–D)"?Tap to revealAnswerThree extensibility approaches — Key User (in-app), Developer (on-stack ABAP Cloud), Side-by-side (BTP) — and a separate cleanliness scale, Levels A (released/stable) to D (modifications/table writes); use the lowest-effort approach and aim for Level A.
• QuestionIn "Extensibility approaches and clean-core levels (A–D)", explain:Tap to revealAnswerThree approaches (not tiers): Key User (in-app low-code, on-stack), Developer (pro-code on-stack ABAP Cloud / Embedded Steampunk), Side-by-side (decoupled on BTP).
• QuestionIn "Extensibility approaches and clean-core levels (A–D)", explain:Tap to revealAnswerSide-by-side is a cleanest-core option for a separate lifecycle/runtime — not the 'worst' last resort.
• QuestionIn "Extensibility approaches and clean-core levels (A–D)", explain:Tap to revealAnswerClean-core levels (Aug 2025): A = released/stable APIs (on-stack or BTP), B = released classic APIs too, C = accesses SAP internal objects, D = modifications/table writes/implicit enhancements (not clean).
• QuestionIn "Extensibility approaches and clean-core levels (A–D)", explain:Tap to revealAnswerPick the lowest-effort approach that meets the requirement; aim for Level A.
• QuestionAnalogy for "Extensibility approaches and clean-core levels (A–D)":Tap to revealAnswerKey User is rearranging the furniture, Developer is a permitted renovation, Side-by-side is a separate annex with its own utilities — and Levels A–D grade how cleanly any of them was built.
• QuestionWhat is "Restricted ABAP — what changes"?Tap to revealAnswerSet a package to 'ABAP for Cloud Development' and the compiler itself blocks non-Clean-Core code — only released APIs compile.
• QuestionIn "Restricted ABAP — what changes", explain:Tap to revealAnswerRestricted ABAP is set per package via the ABAP language version.
• QuestionIn "Restricted ABAP — what changes", explain:Tap to revealAnswerOnly released (C1) objects compile; classic statements (WRITE, CALL TRANSACTION, EXEC SQL, macros) are syntax errors.
• QuestionIn "Restricted ABAP — what changes", explain:Tap to revealAnswerCompile-time enforcement is stronger than an ATC finding you can ignore.
• QuestionIn "Restricted ABAP — what changes", explain:Tap to revealAnswerATC variant ABAP_CLOUD_DEVELOPMENT_DEFAULT is the practical source of truth for what's allowed.
• QuestionAnalogy for "Restricted ABAP — what changes":Tap to revealAnswerIt's a spell-checker that refuses to save the document until the forbidden words are gone.
• QuestionWhat is "Release contracts: C0 / C1 / C2 / C3"?Tap to revealAnswerC1 = released and upgrade-stable (safe to use); C0/C2/C3 = internal, unstable, or deprecated (don't build on them).
• QuestionIn "Release contracts: C0 / C1 / C2 / C3", explain:Tap to revealAnswerC0 not released · C1 released (cloud-safe) · C2 use-system-internal (unstable) · C3 deprecated.
• QuestionIn "Release contracts: C0 / C1 / C2 / C3", explain:Tap to revealAnswerOnly C1 is safe to consume from a Clean Core package.
• QuestionIn "Release contracts: C0 / C1 / C2 / C3", explain:Tap to revealAnswerAPI State is visible per object in ADT and browsable at api.sap.com.
• QuestionIn "Release contracts: C0 / C1 / C2 / C3", explain:Tap to revealAnswerA C1 API can still leak a C2 type — consuming that type is a violation ATC flags.
• QuestionAnalogy for "Release contracts: C0 / C1 / C2 / C3":Tap to revealAnswerC1 is a published, supported API; C2 is an undocumented internal function you found by reading the source.
• QuestionWhat is "The software-component boundary"?Tap to revealAnswerThe 'ABAP for Cloud Development' restriction is set per software component and applies to all of it — isolate legacy code in its own component behind a released interface.
• QuestionIn "The software-component boundary", explain:Tap to revealAnswerThe API restriction applies to the whole software component — no mixing.
• QuestionIn "The software-component boundary", explain:Tap to revealAnswerIsolate unavoidable classic code in its own component behind a released interface.
• QuestionIn "The software-component boundary", explain:Tap to revealAnswerCross-component calls obey the consumer's release contract.
• QuestionIn "The software-component boundary", explain:Tap to revealAnswerThe component boundary is where you declare and document what's exposed.
• QuestionAnalogy for "The software-component boundary":Tap to revealAnswerA clean room and a workshop are separate rooms with one controlled doorway — not one room with a line painted on the floor.

1. 1Diagram the core idea

   Analyse~10 min

   In your own words, diagram the central idea of "What Clean Core actually means". Aim for one paragraph, no jargon you haven't earned.

   Done when: A non-expert could read your paragraph and explain it back to you.

   Re-read the source concept

2. 2Translate it to a real situation

   Apply~15 min

   Find a real situation from your own work / life where "The software-component boundary" applies. Translate the idea — describe the situation, the move you'd make, and the alternative you considered first.

   Done when: You can name a specific situation (not a hypothetical), state your move, and explain the trade-off in one paragraph.

   Re-read the source concept

3. 3Teach it back

   Evaluate~5 min

   Pick someone (a colleague, a peer, a rubber duck) and explain the section to them in under 5 minutes. Use your own example, not the one from the lesson.

   Done when: Your listener can repeat the core idea + the trade-off back to you without prompting.

Why this matters. Reading + quizzing prove recall; applying it in a real situation is the only evidence of transfer. Treat at least one of these as non-negotiable before you move on.