6 Challenges That Stall Every S/4HANA Migration

SAP has set a hard deadline: ECC reaches end of mainstream maintenance in 2027. Every SAP customer must migrate to S/4HANA. But the migration itself isn’t the hard part — the custom code is.

Here are the six specific challenges that stall nearly every migration — and what they have in common.

1. Custom ABAP remediation

Millions of lines of custom code must be analyzed, refactored for S/4HANA compatibility, or rewritten entirely. Many custom programs use deprecated APIs, obsolete data models, or SAP-specific patterns that have no S/4HANA equivalent. This isn’t a find-and-replace exercise — it’s a re-engineering project hiding inside a migration project.

2. Business process disruption

Custom transactions and workflow variants that employees rely on daily don’t survive the migration. Teams lose productivity during the gap between decommissioning old processes and standing up new ones. The business doesn’t pause while IT migrates.

3. Integration breakage

Custom RFCs, BAPIs, and middleware interfaces that connect SAP to other enterprise systems need to be re-architected. Every custom integration point is a potential failure during cutover. The more connected your SAP environment, the higher the risk.

4. The re-customization cycle

This is the one nobody wants to talk about. After spending years migrating to clean S/4HANA, business requirements immediately push teams to start customizing again — restarting the same cycle that made the upgrade painful in the first place. You don’t just need to migrate. You need to break the pattern.

5. User adoption friction

SAP Fiori apps deliver a standard UX that doesn’t match how teams actually work. Users resist the migration because the new interface feels like a downgrade from the custom screens they’ve used for years. Technical success means nothing if users won’t adopt.

6. ABAP talent scarcity

The developers who built the original customizations have retired or moved on. Organizations face a shrinking talent pool for ABAP skills at the exact moment they need them most — driving up costs and extending timelines.

What these challenges have in common

Every one of these problems traces back to the same root cause: customization lives inside SAP. Custom code, custom interfaces, custom workflows, custom transactions — all embedded in the core, all blocking the upgrade path.

We wrote a full breakdown of this approach — including nine specific SAP processes that are better built outside the core and an architecture for running ECC and S/4HANA in parallel during migration — in our white paper: The Customization Layer for SAP.