Terminology note: the former 3-tier extensibility model is superseded by the clean core level concept (A, B, C, D). Migration is no longer "get everything to Tier 1" — it is "eliminate Level D, minimize Level C, accept stable Level B, target Level A for new work". See the

abap-cloud

skill for the level definitions.

1. Assess current state: run ATC clean core checks on existing code
2. Classify findings by level: priority 1 → Level D, priority 2 → Level C, priority 3 → Level B
3. Prioritize remediation: Level D first (must fix), then Level C (minimize), then Level B (monitor)
4. Choose a transformation option: retire · renovate side-by-side · renovate on-stack · adapt
5. Implement replacements: released APIs, classic APIs, or wrappers with a single ATC exemption
6. Validate: re-run ATC checks, verify no priority 1/2 findings remain, test functionality

1. In ADT: right-click package → Run As → ABAP Test Cockpit
2. Use check variant

   ABAP_CLEAN_CORE_DEVELOPMENT

   (SAP-delivered) or build a variant from

   ABAP_CLOUD_DEVELOPMENT_DEFAULT

   including:

   • SYCM_USAGE_OF_APIS

     — released/classic API classification, SQL on SAP tables, SAP form routines

   • SYCM_ALLOWED_ENH_TECHNOLOGY

     — enhancement technology compliance

   • CI_SEARCH_CUST_MODIFICATIONS

     — modifications

   • CI_CRITICAL_STATEMENTS

     — critical statements

   • SLIN_SEC

     — Code Vulnerability Analyzer (additionally recommended)
3. Use

   ABAP_CLOUD_READINESS

   to verify ABAP Cloud rules before switching an object's language version
4. Review findings in the ATC Results view

If

SYCM_USAGE_OF_APIS

or

SYCM_ALLOWED_ENH_TECHNOLOGY

are unavailable, implement SAP Note 3565942.

1. Level D — eliminate entirely
   • No modifications → use BAdIs
   • No implicit or explicit enhancements → use BAdIs
   • No direct write access to SAP DB tables → released or classic APIs
   • No not-recommended (

     noAPI

     ) APIs → released or classic APIs
   • Remove critical ABAP statements → released or classic APIs
   • Do not call form routines within SAP programs → released or classic APIs
2. Level C — minimize as much as possible
   • No direct read access to SAP tables → released or classic CDS views
   • Replace SAP internal APIs with released or classic APIs
   • If internal APIs are still needed, explore the changelog for SAP objects for incompatible changes
   • Wrap remaining internal objects and create a single fine-grained ATC exemption
3. Level B — monitor
   • Adopt successors for deprecated API findings
   • Monitor when SAP releases an equivalent API, then migrate to Level A
   • Do not rewrite stable classic code without a business reason
4. Level A — sustain
   • Enforce with

     S_ABPLNGVS

     authorization and separate software components

SUSG

SCMON

Recommendation: leave behind as much legacy code as possible during the conversion — cleaning up afterwards costs significantly more.

• Deletion of objects (e.g., function modules)
• Renaming or deletion of function module parameters
• Incompatible changes to parameter types
• Renaming or deletion of methods in SAP classes
• Removal of fields from CDS views

FUNC

CLAS

INTF

STOB

BDEF

1. Download the Simplification Database file from the SAP Software Download Center (SAP Support Portal)
2. Import it via transaction

   SYCM

3. Run the changelog ATC check during development, or before the system upgrade like other simplification item checks
4. Refactor affected usages toward released or classic APIs

• Wrapping a classic API (Level B object) → the wrapper is Level B
• Wrapping an internal object (Level C object) → the wrapper is Level C
• Wrapping a not-recommended (

  noAPI

  ) object → Level D, do not build it

1. Go to API State tab
2. Add Use System-Internally (C1) contract
3. Set visibility to Use in ABAP Cloud

• Classic APIs often check non-released authorization objects, which cannot be used in ABAP Cloud. PFCG roles may mix released and non-released authorization objects.
• Provide

  SU22

  data for the wrapper when releasing it, and create

  SU22

  variants for each designated usage so roles can be maintained.
• Create a single fine-grained ATC exemption on the wrapper's internal usage rather than one per call site.
• Retire the wrapper once SAP releases the API — replace it and move the code to the ABAP Cloud software component.

• CDS views: create a custom CDS view on top of the non-released SAP CDS view and release it. Association targets and value help views may also need wrappers. If no SAP CDS view exists at all, wrap the database table.
• Classes / interfaces: wrap the non-released FM or class. Do not copy non-released data types (data elements, structures, table types) used in the signature — wrap them via

  TYPES

  declarations in the wrapper's public section, so only the wrapper needs releasing.

1. Released Object Search:

   Ctrl+Shift+A

   → Filter by "Released" APIs
2. API State Filter: In Project Explorer, filter by C1 release state
3. ABAP Element Info: Hover over a non-released object → see successor suggestion if available

F5865

• Search by classic object name
• Filter by release state (C1, C2)
• View successor information

• Classic APIs (Level B):

  objectClassifications_SAP.json

  — viewer at https://sap.github.io/abap-atc-cr-cv-s4hc/?version=objectClassifications_SAP.json
• Not recommended (Level D): filter the viewer for

  state

  =

  noAPI

• Internal with successor (Level C): flagged

  internalAPI

• Anything unclassified and not released defaults to Level C

1. Run ATC clean core checks (

   ABAP_CLEAN_CORE_DEVELOPMENT

   ) on the package/objects
2. Export findings and group by ATC priority → clean core level (P1=D, P2=C, P3=B)
3. Eliminate all Level D findings (priority 1):
   • Remove modifications → use released or classic BAdIs
   • Remove implicit/explicit enhancements → use BAdIs
   • Remove direct write access to SAP tables → released or classic APIs
   • Replace

     noAPI

     object usage → check successor information
   • Remove critical ABAP statements
   • Remove calls to SAP form routines
4. Minimize Level C findings (priority 2):
   • Replace direct read access to SAP tables → released or classic CDS views
   • Replace SAP internal APIs → released or classic APIs
   • For unavoidable internal usage: wrap + single ATC exemption
   • Import the changelog for SAP objects via

     SYCM

     and check for incompatible changes
5. Review Level B findings (priority 3):
   • Adopt successors for deprecated APIs
   • Leave stable classic API usage as-is
6. For each non-released API without a replacement:
   • Create a wrapper in the classic ABAP component and release it for ABAP Cloud
   • Provide

     SU22

     data and variants for the wrapper
7. For each incompatible language construct: refactor to a cloud-compatible alternative
8. For Dynpro/ALV/list-based UIs: plan the Fiori replacement (separate project)
9. Move migrated objects to the ABAP for Cloud Development software component
10. Run

    ABAP_CLOUD_READINESS

    before switching an object's language version
11. Re-run ATC checks — no priority 1 or 2 findings should remain
12. Configure ATC transport settings to block release on priority 1 and 2 findings
13. Execute regression tests

• Current clean core level: [A / B / C / D] (lowest level used)
• Level D findings (must fix): [list]
• Level C findings (minimize): [list]
• Level B findings (monitor): [list]
• Incompatible constructs: [list]
• Estimated effort: [low / medium / high]

• Achievable clean core level: [A / B]
• Residual exemptions required: [list with justification]

undefined

• Clean Core Extensibility Whitepaper — the authoritative source for the level concept
• Extend SAP S/4HANA in the cloud and on premise with ABAP based extensions (Version 2.3, August 2025)
• Custom Code Migration Guide: https://help.sap.com/docs/abap-cloud/abap-development-tools-user-guide/custom-code-migration
• ABAP Cloud API Release Info: https://help.sap.com/docs/abap-cloud/abap-rap/released-abap-objects
• Cloudification Repository: https://github.com/SAP/abap-atc-cr-cv-s4hc
• Wrapper Pattern: https://github.com/SAP-samples/abap-cheat-sheets/blob/main/19_ABAP_Cloud.md
• ATC Cloud Readiness: https://help.sap.com/docs/abap-cloud/abap-development-tools-user-guide/checking-abap-cloud-readiness
• SAP Note 3565942 — clean core ATC checks
• SAP Note 3578329 — classic technology classification

• Remediation checklist: Read

  references/migration-checklist.md

  for the full level-based remediation checklist, effort estimation, and rollback planning

• abap-cloud: Use for clean core level definitions, development models, and wrapper classification
• atc-cloudification: Use for configuring ATC clean core checks and level governance
• released-abap-classes: Use for finding Level A released API replacements
• badi-enhancement: Use for replacing modifications and enhancements with BAdIs
• abap-sql-amdp: Use for modernizing ABAP SQL and AMDP during migration