Capstone A — From 0 to ATC-green
What you'll learn
Scope with SCMON, escalate ATC variants DEFAULT to READINESS to CLOUD behind baselines with named owners, decide wrap-versus-rewrite per API, and govern decommissioning and business comms — fix code last, not first.
- Scope first with SCMON over a 1-3 month window to find the code that is actually executed.
- Escalate ATC variants deliberately: DEFAULT, then S4HANA_READINESS_2023, then ABAP_CLOUD_DEVELOPMENT_DEFAULT.
- Gate each stage with a baseline plus an exemption process owned by named people.
The scenario: you inherit a four-million-line custom codebase on ERP 6 EHP8 that is about to migrate to S/4HANA 2023, and you must define a twelve-month roadmap through a Clean Core lens. The trap is to start fixing code; the architect's job is to scope, sequence, and govern before a single line is touched, because at this scale effort spent on dead or low-risk code is effort wasted.
Scoping comes first: deploy SCMON on the productive system for a representative window — one to three months — so the roadmap targets what is actually executed rather than the whole inventory. The check strategy then escalates deliberately through ATC variants: DEFAULT for a broad first pass, S4HANA_READINESS_2023 for migration-specific Simplification findings, and ABAP_CLOUD_DEVELOPMENT_DEFAULT for code heading to developer extensibility. Each escalation is gated by a baseline and an exemption process with named owners, so the team only ever chases new debt.
The remaining deliverables turn analysis into decisions. A decoupling-cockpit matrix records, per standard API touched, whether you wrap it (a Z facade for cheap future-proofing) or rewrite it to a released equivalent. A decommission policy governs unused code — mark, watch one more cycle, then delete — and a communication plan warns business owners of any behavioural change before it ships. The named-owner governance on baselines and exemptions is what keeps a twelve-month programme honest.
Key points
- Scope first with SCMON over a 1-3 month window to find the code that is actually executed.
- Escalate ATC variants deliberately: DEFAULT, then S4HANA_READINESS_2023, then ABAP_CLOUD_DEVELOPMENT_DEFAULT.
- Gate each stage with a baseline plus an exemption process owned by named people.
- Use a decoupling-cockpit matrix to decide wrap-versus-rewrite per standard API.
- Set a decommission policy (mark, watch a cycle, delete) and a business-comms plan for behavioural change.
Source notes: clean-core-curriculum §14.1
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