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 | Aspect | Brownfield | Greenfield | Bluefield | |--------|-----------|-----------|----------| | Data migration | Automatic (SUM/DMO) | Manual (LTMC) | Selective | | Configuration | Carried over | Redesigned | Mix | | Custom code | Must remediate | Can replace with standard | Must remediate | | Project duration | Shorter | Longer | Longest | | Risk | Medium | Lower (for processes) | High (complex) | | Best for | Large existing systems | Major transformation | Demerger / consolidation | --- ## 2. SAP Readiness Check — Critical Simplification Items ### FI / Accounting | Item ID | Impact | Description | Resolution | |---------|--------|-------------|-----------| | S4TWL_ACDOCA | High | Universal Journal mandatory; BSEG becomes secondary | Ensure New GL active; run Universal Journal migration | | S4TWL_NEWGL | High | Classic GL not supported — New GL must be active | Activate New GL in ECC before SUM run | | S4TWL_ASSETACCTG | High | New Asset Accounting mandatory; Classic AA removed | Run RAALTD01 migration report; verify parallel ledgers | | S4TWL_MATERIAL_LEDGER | High | Material Ledger is mandatory in S/4HANA | Activate ML in ECC first if possible | | S4TWL_BP | High | Business Partner mandatory; vendor/customer must become BP | Run BP migration (FLBPD1/FLBPD3) before conversion | | S4TWL_COFI_RECONCILIATION | Medium | FI-CO reconciliation ledger removed | Ensure no open reconciliation items | ### MM / Logistics | Item ID | Impact | Description | Resolution | |---------|--------|-------------|-----------| | S4TWL_INVENTORY | High | Inventory tables restructured; MBEW→ACDOCA | No direct MBEW access — use CDS | | S4TWL_PLANT | High | Valuation area must equal plant (1:1) | Consolidate if multiple valuation areas per plant | | S4TWL_CENTRALPURCHORG | Medium | Central purchasing org restrictions | Review org structure | ### SD / Revenue | Item ID | Impact | Description | |---------|--------|-------------| | S4TWL_SD_CRM | Medium | CRM integration changes | Review CRM integration scope | | S4TWL_REVENUE_RECOGNITION | High | VBREVN replaced by IFRS 15 POB approach | Design POB-based revenue recognition | ### ABAP / Custom Code | Item ID | Impact | Description | |---------|--------|-------------| | S4TWL_COMPATIBILITY_SCOPE | High | Defines which classic APIs still supported | Run ATC check to identify custom code impact | --- ## 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 | Error | Root Cause | Fix | |-------|-----------|-----| | "Duplicate BP for vendor" | Vendor already linked to a BP | Check existing BP link: LFA1-BKVID | | "Number range not defined" | BP grouping number range missing | BUBA → maintain number ranges | | "Missing mandatory field" | BP grouping requires field not in vendor | Map fields in customizing | --- ## 4. Custom Code Remediation (ATC — ABAP Test Cockpit) ### Most Common ATC Findings | Finding | Root Cause | S/4HANA Replacement | |---------|-----------|---------------------| | SELECT from BSEG | Table no longer primary storage | CDS: `I_JournalEntryItem` | | SELECT * from MARA | Performance + table changes | Targeted CDS with specific fields | | SELECT from MKPF/MSEG | MATDOC is new primary | CDS: `I_MaterialDocumentItem` | | SELECT from BSID/BSAD | ACDOCA is source | CDS: `I_CustomerLineItem` | | SELECT from BSIK/BSAK | ACDOCA is source | CDS: `I_SupplierLineItem` | | CALL TRANSACTION | Compatibility issues | BAPI or RAP action | | Logical database PNPCE | Deprecated | Direct SELECT + AUTHORITY-CHECK | | Old BAdI (CL_EXITHANDLER) | Classic BAdI | New BAdI (GET BADI / SE19) | | Non-Unicode strings | S/4HANA is Unicode-only | String templates `\|...\|` | ### 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