What Actually Breaks During Large-Scale S/4HANA Conversions (And How to Prevent It)

Broken Custom ABAP Code in S/4HANA From an engineer’s vantage point, one of the first headaches in a brownfield S/4HANA conversion is custom ABAP code that no longer runs correctly. S/4HANA isn’t a mere upgrade; it introduces a new   architecture with a simplified data model and revised logic. Many classic tables and transactions simply vanish or behave differently. As a result, existing Z-programs can dump or produce wrong results what worked fine in ECC may outright fail in S/4HANA, potentially breaking core business processes. Common breakage patterns include: