Clean Core tiers
Clean Core extensibility tiers (Tier 1–3)
Also known as: 3-tier extensibility model
SAP’s three-tier model for extensions: Tier 1 uses only released APIs (ABAP Cloud), Tier 2 wraps classic functionality, Tier 3 is classic custom code.
Tier 1 — cloud-ready extensions. Developed with ABAP Cloud or side-by-side, using only released APIs and extension points. Upgrade-stable.
Tier 2 — cloud API enablement. Wrappers around classic, not yet released functionality that expose it to Tier 1 code in a controlled way. Tolerated as a bridge; replace a wrapper with a Tier 1 solution once SAP releases a successor.
Tier 3 — classic ABAP extensions. Code that uses unreleased objects, reads or writes SAP tables directly or modifies standard code. This is where upgrade risk concentrates.
SAP has since refined the guidance into more granular clean core levels. The SAP release data behind ERP Preflight carries a clean core level per object where SAP publishes one.
In ERP Preflight
Clean Core Object Guard reports Tier 3 patterns such as direct table access and use of unreleased objects. SAP Gap Radar uses its own 12-step scale to rank how a requirement can be met, from a standard scope item to a Clean Core violation.
Problems that involve Clean Core tiers
- MajorCustom Z/Y transaction needs Clean Core review
- BlockerDirect write to an SAP standard table
- CriticalDirect read of an SAP standard table
- CriticalObsolete or cloud-forbidden ABAP statement
- CriticalCall to a function module not released for cloud development
- CriticalUse of a class not released for cloud development
- MajorUse of a deprecated SAP object
- MajorDynamic call target cannot be verified
Related terms
Free tools
- Clean Core Object Lookup
Is a table, CDS view, class or function module released for ABAP Cloud?
Background articles
- Clean core extensibility explained: tiers, released APIs and classic modificationsA practical overview of how SAP classifies extensions by their upgrade stability, from ABAP Cloud on released APIs to classic modifications, and how to assess existing custom code.
Written for ERP Preflight · reviewed September 27, 2026
All glossary termsERP Preflight is independent and not affiliated with SAP SE. SAP, ABAP, Fiori and S/4HANA are trademarks of SAP SE.