Three S/4HANA Migration Risk Factors That Sink Projects

Arjun Mehta breaks down what you need to know

After 25 years of SAP implementations, I’ve watched too many S/4HANA migrations go sideways for the same three reasons: data complexity, custom code impact, and underestimated testing scope. Teams treat the move as a technical upgrade, then discover halfway through cutover that the system is full of legacy garbage, half the custom programs don’t work, and nobody planned for business process regression. Let me be blunt: this is not an upgrade. It’s a transformation program.

The Real Story

The three risk factors don’t exist in isolation—they compound each other. Here’s what I’ve seen repeatedly across dozens of projects, from mid-size manufacturers to global logistics firms.

Data complexity. Your ECC system has been running for 10, 15, even 20 years. Tables like MSEG, LIPS, and CDPOS haven’t been archived because “disk is cheap.” Master data has duplicates, inconsistent material groups, and vendor records that haven’t been used since R/3 4.6C. In S/4HANA, the data model changes fundamentally—MSEG and LIPS are aggregated into MATDOC, for example. The migration itself forces you to reconcile and transform that data. If you haven’t profiled volume and quality months before cutover, you will hit surprises.

I recall a project where the client had 4.2 billion records in MSEG. Nobody did archiving beforehand because they assumed the HANA database could handle it. Cutover ran 60 hours over schedule because the data conversion jobs choked on millions of duplicate material document lines that should have been archived a decade ago.

Custom code impact. Most ECC landscapes are littered with Z programs, user exits, BAdIs, and implicit enhancements. Some are critical, many are dead weight. S/4HANA doesn’t just replace transactions—it changes underlying data structures, BAPIs, and even the ABAP programming model. Code that worked fine on ECC may reference obsolete tables (like MBEWH or old BSEG fields), call BAPIs that no longer exist, or rely on transaction codes that have been replaced.

A classic example: a custom goods movement program that used BDC on MB1B. In S/4HANA, MB1B is gone. The program failed during integration testing, and the team had to scramble to rewrite it using the new “Material Documents – Create” BAPI. That cost two weeks. And it was entirely predictable if they had run SAP Readiness Check and ABAP Test Cockpit early.

Testing scope. Even teams that get data and custom code right often test only standard smoke scenarios. S/4HANA migration needs three testing tracks: business process regression (does the end-to-end flow still work?), migration validation (data reconciliation between source and target at field level), and performance testing (do your heavy MRP runs or month-end close actually complete under HANA?). Ignoring any one of these is a recipe for post-go-live chaos.

What This Means for You

For consultants and architects

References

• Common Risks in S/4HANA Migration & How to Overcome
• SAP HANA Platform Overview- SAP S/4HANA Product Information

References

• SAP S/4HANA Product Information
• SAP HANA Platform Overview
• Common Risks in S/4HANA Migration & How to Overcome