SAP S/4HANA Migration Services
SAP ECC mainstream maintenance ends in 2027, with extended maintenance available to 2030. That is a firm deadline for a project most organisations underestimate, and the specialist capacity to do it is finite.
CssInfotech delivers S/4HANA migrations by all three routes — brownfield system conversion, selective data transition, and greenfield re-implementation — starting with an honest readiness assessment rather than a predetermined answer.
Brownfield, Greenfield or Selective Data Transition?
Any partner who recommends a route before running a readiness check is guessing. That said, here is the honest comparison we work from.
| Factor | Brownfield (system conversion) | Greenfield (new implementation) | Selective data transition |
|---|---|---|---|
| What happens | Existing system converted in place | New system built, selected data migrated | New system, chosen entities and history moved |
| Keeps configuration | Yes, including the awkward parts | No - designed fresh | Selectively |
| Keeps history | All of it | Only what you migrate | As much as you choose |
| Process redesign | Limited - you carry existing processes | Full opportunity to reset | Targeted redesign where wanted |
| Custom code | Must be remediated | Rebuilt only where justified | Rebuilt selectively |
| Typical duration | Shorter | Longer | Medium to long |
| Change management load | Lower | Highest | Medium |
| Best when | Processes work; you want technical modernisation | Processes are a mess; you want a reset | Multi-entity, carve-out or partial reset |
Our SAP S/4HANA Migration Services
A conversion is a technical project with a large functional shadow. We cover both, plus the analysis that sizes it properly.
Readiness Assessment
Real numbers from your real system, before any commitment.
- SAP Readiness Check 2.0 execution and interpretation
- Simplification Item Check with relevance analysis
- Custom code analysis via ABAP Test Cockpit remote checks
- Add-on, business function and integration compatibility review
- Sizing, effort estimate and route recommendation with reasoning
Brownfield System Conversion
In-place conversion, rehearsed until the downtime is predictable.
- Maintenance Planner, stack generation and prerequisite handling
- Software Update Manager with Database Migration Option (DMO)
- SPDD and SPAU dictionary and repository adjustment
- Multiple full dress rehearsals against production copies
- Downtime-optimised conversion where the window is tight
Mandatory Data Conversions
The prerequisites that catch unprepared projects.
- Customer/Vendor Integration (CVI) to Business Partner
- New Asset Accounting migration
- Material ledger activation and inventory valuation changes
- Universal Journal (ACDOCA) migration and reconciliation
- Credit management and output management transitions
Custom Code Remediation
Usually the largest workstream. Usually smaller than feared.
- Usage data to identify and delete genuinely dead code
- Fixes for data model changes: MATNR, Business Partner, ACDOCA
- Replacement of removed transactions and obsolete modules
- HANA performance remediation for problem SQL patterns
- Detailed remediation backlog with per-object estimates
Testing & Validation
Prove nothing broke — that is the entire objective of a conversion.
- Regression test scope built from actual process usage
- Financial reconciliation before and after conversion
- Integration testing across every interface
- Performance testing at realistic volume
- Business-owned user acceptance testing
Cutover & Post Go-Live
A rehearsed runbook, and support through the first close.
- Hour-by-hour cutover runbook with named owners
- Go / no-go criteria and a tested rollback position
- Command centre coverage through the conversion weekend
- Hypercare through the first full period close
- Post-conversion optimisation and Fiori rollout planning
Our Migration Process
The single most valuable thing we do is rehearse. By the production conversion weekend we want zero surprises left.
- AssessReadiness Check, simplification items, custom code analysis and add-on compatibility. Output is a route recommendation with evidence and a costed estimate.
- PreparePrerequisite work in the existing ECC system — CVI, housekeeping, archiving, dead code deletion. Doing this early shortens every later run.
- First conversion runA sandbox conversion on a production copy. This is where the real issues surface, and where the estimate becomes reliable rather than theoretical.
- Remediate & repeatCode and configuration fixes applied, then converted again. We repeat until a run completes cleanly within the target downtime window.
- Test & reconcileFull regression, integration and performance testing plus financial reconciliation, with business sign-off on each process area.
- Convert productionThe rehearsed runbook executed over the agreed window, with a command centre, defined go/no-go gates and hypercare immediately after.
The Prerequisites That Derail Unprepared Conversions
None of these are optional, and every one of them takes longer than teams expect. Starting them early is the cheapest risk reduction available.
- Business Partner conversion (CVI) — customers and vendors must become Business Partners first
- New Asset Accounting — mandatory in S/4HANA, with its own migration steps
- Material number length — custom code assuming 18 characters needs review
- Add-on compatibility — every add-on needs an S/4HANA-certified version
- Industry solution support — not all ECC industry solutions have equivalents
- Archiving and housekeeping — less data means shorter, safer downtime
- Unicode conversion — still a prerequisite on older systems
- Custom code cleanup — delete the unused before paying to fix it
Why the 2027 Deadline Is Closer Than It Looks
There is no need for panic, but there is a real case for starting the assessment now rather than next year.
The timeline arithmetic
Mainstream maintenance for SAP ECC ends at the end of 2027, with extended maintenance available at a premium through 2030. A mid-sized conversion, done properly with rehearsals and testing, takes twelve to eighteen months. Add the time to build a business case, secure budget and select a partner, and a 2027 target means deciding now.
- Assessment and business case: 2 to 3 months
- Budget approval and partner selection: 2 to 4 months
- Preparation and prerequisite work: 3 to 6 months
- Conversion, testing and rehearsals: 6 to 12 months
- Hypercare and stabilisation: 2 to 3 months
The constraint nobody plans for
Experienced conversion capacity is finite, and it is being consumed steadily as the deadline approaches. The customers who leave it latest will face both the highest rates and the least experienced available teams.
- Skilled conversion specialists are already in short supply
- Extended maintenance to 2030 costs a premium on top of support
- Late programmes get compressed testing, which is where risk lives
- Early movers can phase work across multiple budget years
- An assessment is cheap and does not commit you to a route
Tools & Technologies We Use
Conversions are tool-heavy. Knowing which tool answers which question is most of the skill.
Assessment
- SAP Readiness Check 2.0
- Simplification Item Check
- ABAP Test Cockpit
- Custom Code Migration app
- SQL Monitor (SQLM)
- Usage Procedure Logging (UPL)
- Maintenance Planner
- SAP Transformation Navigator
Conversion & migration
- Software Update Manager (SUM)
- Database Migration Option (DMO)
- Downtime Optimized Conversion
- near-Zero Downtime Maintenance
- SAP Migration Cockpit
- CVI (Business Partner)
- SAP Data Services
- SLT
Testing & operations
- Solution Manager
- SAP Cloud ALM
- Focused Run
- ChaRM
- Tricentis / eCATT
- HANA Studio
- DBACOCKPIT
- SAP Fiori apps library
Why Choose CssInfotech for Your Migration
A conversion is not a good place for optimism. Our value is in being realistic early, when there is still time to act on it.
Assessment before recommendation
We do not have a house preference for brownfield or greenfield. We run the readiness check, look at your custom code and processes, and recommend based on evidence.
We rehearse until it is boring
Multiple sandbox conversions on production copies. The production weekend should contain no new information, and that only comes from repetition.
Custom code realism
We start by measuring what is actually used. Deleting dead code routinely removes a large share of apparent remediation scope, which is a direct saving.
Functional and technical in one team
A conversion is not just a technical upgrade — Business Partner, asset accounting and the Universal Journal all need functional design. We staff both sides.
Downtime engineering
Where your window is genuinely tight, we use downtime-optimised approaches and archiving to fit it, rather than asking the business to accept a longer outage.
We are there at close
Hypercare covers the first full period close. That is when finance discovers whether the conversion really worked.
SAP S/4HANA Migration FAQs
What exactly happens in 2027?
Mainstream maintenance for SAP ECC 6.0 ends on 31 December 2027. After that you can buy extended maintenance at a premium through the end of 2030, and beyond that customer-specific maintenance, which does not include new legal or regulatory updates. For most organisations, especially those with statutory reporting obligations, 2030 is the practical hard stop.
How long does a brownfield conversion take?
For a mid-sized single-system landscape, typically twelve to eighteen months end to end, of which the technical conversion runs are a small part. The time goes into custom code remediation, prerequisite data conversions, testing and rehearsals. Larger or multi-system landscapes take longer.
How much downtime does the production conversion need?
It depends on database size, hardware and how much you have archived. A well-prepared mid-sized system commonly fits a long weekend. Where that is not acceptable, downtime-optimised conversion and near-Zero Downtime Maintenance can reduce it substantially, at the cost of extra complexity. We establish the real figure during rehearsals rather than promising one up front.
Will we lose our custom code and reports?
No, brownfield conversion keeps your custom objects — but some need remediation to work with the new data model, and some reference transactions or tables that no longer exist. The practical answer is that a meaningful portion should simply be deleted because nobody has run it in years, and the rest gets fixed on a prioritised backlog.
Can we combine conversion with a move to the cloud?
Yes, and many customers do exactly that under RISE with SAP — converting and rehosting to private cloud in one programme. It concentrates the change into one event rather than two, which is usually better for the business, though it does make that single programme bigger. We model both sequences with you.
What does a readiness assessment cost and what do we get?
It is a short, fixed-scope engagement, typically three to five weeks. You get the Readiness Check output interpreted rather than raw, a relevant simplification item list, a custom code remediation backlog with estimates, add-on and integration compatibility findings, a recommended route with reasoning, and a costed programme estimate. It is deliberately structured so you can take it to a different partner if you prefer.
Related SAP Services
Migration programmes normally include several of these workstreams.
Find Out Where You Really Stand on S/4HANA Readiness
Our fixed-scope readiness assessment gives you real numbers from your own system — simplification items, custom code scope, add-on risks and a costed route recommendation you can act on.