SAP Migration · 6 min read · May 2026
Why custom ABAP breaks on S/4HANA and how to prepare
By Thinklytics Partners, SAP S/4HANA Practice
Custom ABAP breaks on S/4HANA because the simplified data model changes tables and structures the code relied on. Inventory, measure usage, and remediate what is used.
Topics covered
- ABAP
- Clean Core
- Custom Code
- S/4HANA
Frequently asked questions
Why does custom ABAP break on S/4HANA?
Because S/4HANA simplifies the data model, changing tables and field structures the old code relied on. Code written against the old structures fails or misbehaves.
How do we prepare custom code for S/4HANA?
Inventory every custom object, measure what is actually used, retire the dead code, and remediate the rest against the new model toward a clean-core approach.
How much custom code is usually dead?
Often a large share. Measuring usage before remediation avoids paying to fix code nobody runs.
What is clean core?
Keeping the S/4HANA core standard and extensions separate, so the system stays upgradable and lower-maintenance. It is the target for custom-code remediation.
Should we remediate everything?
No. Remediate only what is used, against the new model. Remediating blindly recreates the mess you are trying to leave.
Who should do ABAP remediation?
Senior developers who know the simplified data model. It is skilled work, and getting it wrong stalls the migration at cutover.