6 SAP S/4HANA Migration Moves That Actually Work (From the Trenches)

The problem nobody talks about
Most SAP migrations don’t fail because of tech.
They fail because teams underestimate complexity.

I’ve seen projects where:
• Data looked “clean” but broke during migration
• Custom code silently failed post-go-live
• Downtime windows got blown out by hours
And the worst part? Everything looked “green” in planning.

If you're working on an SAP S/4HANA migration, you already know—this isn’t just an upgrade. It’s a full system rethink.

Let’s break down what works in real-world migrations.

The challenge (in simple terms)
Moving to S/4HANA means:
• Old ERP → New data model
• Custom code → Compatibility issues
• Legacy DB → In-memory architecture
• Business processes → Need redesign
So, you're not just migrating data.
You're aligning data + code + business logic + infrastructure all at once.
That’s where most teams struggle.

What we did (step-by-step, real workflow)
Here’s a practical flow we used in a mid-size enterprise migration.

1. System assessment before touching anything
We started with a deep system scan.

Tools used:
• SAP Readiness Check 2.0
• Custom Code Analyzer
• Simplification Item Catalog

What we checked:
• Add-ons compatibility
• Data volume
• Custom code usage
• Business processes impacted

Key insight:
~30% of custom code was unused.
We removed it before migration → saved time + reduced risk.

2. Clean the data (seriously, don’t skip this)
Data migration is where things break.

We focused on:
• Removing duplicates
• Archiving old transactional data
• Fixing inconsistencies

Tools:
• SAP Data Services
• Migration Object Modeler (MOM)

Workflow:
Extract → Clean → Validate → Load (test system)
We ran this cycle multiple times.

Why?
Because your first migration run will fail. That’s normal.

3. Choose the right migration approach
There are 3 main approaches:
• Greenfield → Fresh implementation
• Brownfield → System conversion
• Landscape Transformation → Hybrid
We chose Brownfield.

Why?
• Existing system was stable
• Business didn’t want process changes
• Faster timeline
But we still redesigned some processes later.

4. Fix custom code compatibility
This is where devs come in.
S/4HANA removes/changes many tables and functions.

Example:
• Old table: MKPF, MSEG
• New: MATDOC

What we did:
• Ran custom code checks
• Identified incompatible queries
• Rewrote SQL logic

Key change:
Moved from:
SELECT * FROM MSEG

To:
Use CDS Views / New Data Model

Tools:
• ABAP Test Cockpit (ATC)
• Code Inspector

5. Set up the right architecture
We deployed:
• SAP S/4HANA on HANA DB
• App server + DB server split
• Fiori frontend for UI
Architecture flow:
User → Fiori UI → App Server → HANA DB
Key improvements:
• Real-time reporting
• Faster query execution
• Simplified data model

6. Test like production depends on it (because it does)
Testing wasn’t just QA.
We did:
• Unit testing
• Integration testing
• UAT (User Acceptance Testing)
• Performance testing
Critical step:
Simulate real workloads.

We used:
• Batch job simulation
• High-volume transaction testing

Lesson learned:
Most issues show up only under load.

Real results (what improved)
After go-live:
• Reporting speed improved by ~60%
• Batch jobs ran 40% faster
• Data footprint reduced by 35%
• Custom code reduced by ~30%

But the biggest win?
System became easier to maintain.
Less legacy = fewer surprises.

6 success factors that made the difference

1. Clean before you move
   Don’t migrate garbage.
   Fix data + remove unused code early.

2. Start with system insights
   Use readiness tools.
   Guessing = risk.

3. Don’t blindly keep old processes
   Even in Brownfield, rethink workflows.
   Some legacy processes don’t belong in S/4.

4. Treat custom code as a liability
   Every line of old code = potential failure point.
   Refactor aggressively.

5. Test under real conditions
   Not just “does it run?”

Test:
• Load
• Scale
• Edge cases

1. Involve dev + business together This isn’t just IT. Business logic changes = system changes.

Developer-focused takeaways
If you’re a developer working on S/4HANA:
• Learn CDS Views (they replace heavy SQL usage)
• Understand the new data model (MATDOC, etc.)
• Use ATC early, not late
• Avoid SELECT * — performance matters more now
• Think in terms of data flow, not just tables

Final thought
SAP S/4HANA migration isn’t “hard” because of technology.
It’s hard because everything is connected.
Data → Code → Business → Infrastructure
Miss one, and the whole thing shakes.
Let’s discuss

What’s been the hardest part of your SAP migration so far?
• Data issues?
• Custom code headaches?
• Performance surprises?
Curious to hear real stories from others building in this space.