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Core Migration Principle: High-risk ERP transformations fail when executed as "Big Bang" cutovers. Replacing thousands of lines of procedural ABAP with Clean Core RAP overnight creates catastrophic disruption. Modern enterprise architects use the Strangler Fig Pattern and In-Memory Feature Toggles to route traffic gradually between classic routines and modern cloud services with instant kill-switch capabilities.
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1. The Strangler Fig Pattern in SAP ERP
Originating from software engineering, the Strangler Fig pattern replaces monolithic system components incrementally until the legacy code can be safely retired without an outage:
- Build Modern Replacement in Parallel: Develop the new RAP Business Object and CDS views in pure ABAP Cloud (Language Version 5).
- Quarantine Legacy Logic: Place classic BAPI calls inside an isolated Tier-2 Quarantine Wrapper.
- Deploy Inactive: Import both artifacts to production behind a Feature Toggle set to
Inactive. Zero business risk.
- Canary Rollout: Activate the feature flag for a single pilot company code (e.g., Company Code 1000).
- Compare & Certify: Verify financial postings and reconciliations in parallel.
- Full Cutover & Decommission: Expand to 100% of global subsidiaries, then safely drop the legacy wrapper.
2. Feature Toggles: High-Performance In-Memory Architecture
In high-throughput transactional processes (such as billing runs or sales order creation processing 10,000 items/minute), querying the database table on every feature flag evaluation creates severe database bottlenecks.
The In-Memory Singleton Caching Pattern:
- A singleton class
ZCL_FEATURE_TOGGLE_MANAGER holds an internal hashed table cache.
- The first request per internal session queries persistence via released CDS view entity
ZI_FeatureToggle.
- Subsequent checks are served directly from process memory in less than 0.05 milliseconds.
3. Canary Rollout Scopes
| Rollout Scope |
Implementation Context |
Risk Level |
When to Apply |
| Company Code Filter |
Checks iv_scope_value = '1000' |
Very Low |
Phase 1 pilot subsidiary testing. |
| User Role / Auth Aspect |
Checks if user has authorization object Z_PILOT_USER |
Very Low |
Internal business analyst dark launching. |
| Percentage / Hash |
MOD( HASH( SalesOrderID ), 100 ) < 10 |
Medium |
Statistically distributed canary sampling (10% of orders). |
| Global Cutover |
ScopeValue = '*' |
Production Standard |
Final signoff and global go-live. |
4. The 5-Second Kill Switch
The greatest advantage of Clean Core Feature Flags is the Instant Kill Switch:
- If a zero-day issue occurs post-cutover, administrators simply toggle
IsActive = false via an administrative Fiori app.
- The application immediately falls back to the battle-tested Tier-2 legacy routine on the very next transaction.
- Zero downtime, zero emergency transport creation, zero production freeze.
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