Sap S4 Migration

1. Approach Decision Tree

Q1: Keep existing configuration and historical data?
  YES  → System Conversion (Brownfield)
  NO   → New Implementation (Greenfield)
  SOME → Selective Data Transition (Bluefield / Shell Conversion)

Q2: Target deployment model?
  On-premise        → Full flexibility; custom code with restrictions
  RISE (PCE)        → Managed infrastructure; same S/4HANA functionality
  S/4HANA Cloud PE  → Clean Core only — no modifications, no ABAP CBO

Approach Comparison

2. SAP Readiness Check — Critical Simplification Items

FI / Accounting

MM / Logistics

SD / Revenue

ABAP / Custom Code

3. Business Partner Migration (Mandatory for All Conversions)

Every customer and vendor must be converted to a Business Partner before go-live.

Migration Steps

Step 1: Pre-checks
  PREC_CUST  → customer readiness check
  PREC_VEND  → vendor readiness check
  Fix all errors before proceeding

Step 2: BP configuration
  BUPA_PRE_MERGE → BP grouping and number range configuration
  Define BP grouping: customer grouping / vendor grouping

Step 3: Mass creation
  FLBPD1  → vendor → Business Partner (mass conversion)
  FLBPD3  → customer → Business Partner (mass conversion)

Step 4: Verification
  BP transaction → check grouping, roles (FLVN00 / FLCU00)
  FBL1N / FBL5N → verify AP/AR still works via BP ↔ vendor/customer link

Step 5: Post-migration check
  BUPA_CHECK → Business Partner consistency check
  Reconcile customer/vendor count vs BP count

Common BP Migration Errors

4. Custom Code Remediation (ATC — ABAP Test Cockpit)

Most Common ATC Findings

ATC Check Process

1. SE80 / ATC → run check on custom package
2. Filter results: Priority 1 (blocker) and Priority 2 (high) must be fixed
3. Priority 3/4: fix before go-live but not hard blockers
4. Document findings → assign to developers → track remediation

5. Universal Migration Timeline

Phase 1 — Discover (3–4 weeks)
  □ SAP Readiness Check → download simplification item report
  □ ATC custom code analysis → categorize findings by priority
  □ BP migration pre-checks (PREC_CUST / PREC_VEND)
  □ Fit-gap assessment: standard S/4HANA vs current processes

Phase 2 — Prepare (4–6 weeks)
  □ Solution design per simplification item
  □ BP migration configuration (BUPA_PRE_MERGE)
  □ Custom code remediation (Priority 1 + 2 items)
  □ New GL activation if not already active (ECC)
  □ Material Ledger activation if not active (ECC)

Phase 3 — Realize (12–16 weeks)
  □ DEV system conversion (SUM / DMO tool)
  □ Custom code migration and unit testing
  □ Integration testing (all modules)
  □ Parallel run for financials (if required)
  □ User acceptance testing (UAT)

Phase 4 — Deploy (4–6 weeks)
  □ QAS system conversion
  □ QAS regression testing
  □ Cutover planning and rehearsal
  □ PRD system conversion (go-live weekend)
  □ Hypercare (4 weeks minimum)

6. Post-Migration Validation Checklist

FI:
□ Trial balance matches pre-migration (FS10N)
□ AP open items correct (FBL1N — count and amount)
□ AR open items correct (FBL5N — count and amount)
□ Asset spot check (AW01N — 10% sample of assets)
□ ACDOCA reconciliation report clean

MM:
□ Stock quantities match (MB52 pre vs post)
□ Open PO / GR / IR correct (ME2M)
□ Material prices correct (MM03 → Accounting 1)

SD:
□ Open sales orders correct (VA05)
□ Billing due list correct (VF04)
□ Credit limits migrated (FD32 / UKM_BP)

ABAP:
□ ST22: zero short dumps in first 3 days post go-live
□ SM21: no system error messages
□ Custom reports executed with expected output
□ Background jobs running on schedule (SM37)

7. References

• references/simplification-items.md — top 30 simplification items by module with impact, resolution, effort