How to Run Remote ATC Checks for S/4HANA Custom Code

To run S/4HANA custom code checks with remote ATC, you set up a central check system (S/4HANA 2025, the SAP BTP ABAP environment, or an AS ABAP 7.52 system), connect it to your ECC system over RFC, import the latest Simplification Database, and run the check variant for your target release, such as S4HANA_READINESS_2025. The result is a list of findings: every place your Z code touches something SAP changed or removed in S/4HANA. That list becomes your adaptation worklist, and it also gives you the retest scope for the custom code side of the conversion.

This guide covers the setup, the run, how to read and triage the results, and what evidence a test manager should ask for before signing off the custom code workstream. For where this sits in the full program, see our end-to-end ECC to S/4HANA migration guide.

Readiness Check vs. remote ATC: why you need both

SAP's own FAQ separates the two tools by phase: SAP says to use SAP Readiness Check while you plan, for a high-level view of custom code effort, and ATC during the project, where it performs the deep analysis and finds every critical use of simplified SAP objects. If you have only run the Readiness Check (see how to run and read it), you have an estimate. You do not yet have a worklist that developers can pick up and testers can trace.

Remote ATC also fills a different gap from the Simplification Item Check. The SI-Check looks at data and configuration consistency. ATC looks at your ABAP source code.

Step 1: Start collecting usage data now

The cheapest custom code fix is deleting code nobody runs. The Custom Code Migration Guide for SAP S/4HANA 2025 recommends using the ABAP Call Monitor (SCMON) together with transaction SUSG to collect usage data in production for at least a year. SUSG aggregates that data in production so you can feed it into scoping.

Step 2: Pick and size the central check system

All three options read your ECC code remotely. The difference is whether you get usage-based scoping and the newer tooling.

Central check system	Tool	Usage-based scoping	Notes
SAP S/4HANA 2025 (on-premise)	Custom Code Migration app (Fiori)	Yes	Runs the latest ATC check versions on the ABAP platform
SAP BTP ABAP environment	Custom Code Migration app	Yes	Connects to ECC through Cloud Connector; included in every RISE with SAP subscription
SAP NetWeaver AS ABAP 7.52	ATC transaction (SAP GUI)	No	Cannot filter results by scope or quick fix availability

The options and their limits come from SAP's Custom Code Migration Guide. SAP has also confirmed that the Custom Code Migration app is available in every RISE with SAP subscription. RISE customers should therefore use the BTP route unless they have a reason not to. If you build a dedicated 7.52 ATC system, SAP's sizing guidance is roughly 1 CPU and 4 GB RAM per 16,000 custom objects, plus about 400 kB of database space per object (SAP Community).

Step 3: Connect ECC and load the Simplification Database

SAP Notes

• Collective Notes: 2364916 lists what remote ATC analysis needs in both the central and checked systems. 2436688 lists the Notes for the S/4HANA custom code checks and the Custom Code Migration app (SAP Community). Implement them with their manual steps. Recheck the versions when you start.
• Checked system (ECC): 2270689 delivers the RFC stubs for remote analysis. It points to release-specific Notes for your SAP_BASIS level, so give Basis time to implement it.
• Target-release variant: Note 3666462 brings S4HANA_READINESS_2025 into the central system. Earlier targets have their own Notes, for example 3365357 for 2023 (SAP FAQ).

RFC and system setup (7.52 route)

In transaction ATC, switch the system role to ATC checks using object providers. Then create a system group for each release level and an object provider for each RFC destination to ECC (SAP guide). The RFC connection must work without a logon dialog, and the RFC user in ECC needs the authorizations listed in SAP Note 2672703 (Custom Code Migration Guide 2025).

Simplification Database

Download the latest CCMSIDB content from the SAP Software Download Center (SAP Note 2241080 describes it). Then upload the ZIP file in the central check system with transaction SYCM (SAP). Write down the content version. If it changes between runs, your findings counts will change too.

Step 4: Run the check

1. Collect usageSCMON and SUSG in production, 12 months
2. ConnectRFC, object provider or Cloud Connector, Notes applied
3. Load contentCCMSIDB via SYCM, version recorded
4. Run variantS4HANA_READINESS_2025 against ECC
5. Triage and fixScope, delete, quick fix, adapt
6. RetestRe-run ATC, then functional tests

In the Custom Code Migration app: create a project and set the transition scenario, the target release and the material number length (SAP). The material number setting matters if you plan to use the 40-character MATNR. Upload your usage data and the app calculates a default scope. It can also create a deletion transport that removes unused code during the conversion.

In ATC on 7.52: schedule a run series that uses the readiness variant and your ECC object provider. Use the release-specific variant, not S4HANA_READINESS_REMOTE. According to SAP, the release variants check only the simplification items for that target release, while the REMOTE variant checks every item in the Simplification Database.

If runs time out or throw RFC errors, SAP KBA 3794349 usually traces the cause to missing Notes in the checked system, such as 2270689 and the ATC stub enhancement in 3678290.

Step 5: Triage findings into fix, delete or accept

Each finding points to a simplification item and its SAP Note, such as reads and writes on MKPF/MSEG (now MATDOC), pricing reads on KONV, or the removed data element FILE. Sort the list three ways:

• Delete: code with no usage, after the process owners approve.
• Quick fix: mechanical changes. In ABAP Development Tools, findings with a deterministic quick fix show a yellow light bulb (SAP). In October 2026, SAP added a Transferable Quick Fix filter to the Custom Code Migration app for findings you can fix in ECC before the conversion (Note 3756014 required in ECC). That matters for cases like FILE, which no longer exists in S/4HANA, so the copy has to be created in ECC first (SAP).
• Manual adaptation: logic changes, such as replacing direct table updates with released APIs.

SAP now also offers the S/4HANA Custom Code Migration Agent in Joule for Developers. It runs the readiness checks, applies quick fixes in batch, and proposes AI fixes with confidence scores. SAP's own description still leaves developers to review the changes and activate the objects. For a test lead, AI-adapted code is changed code and gets the same functional retest as anything a person wrote.

Step 6: Turn the worklist into test scope and sign-off evidence

In a conversion, ATC findings carry through to the SPDD and SPAU adjustments and to a re-run of ATC in the converted sandbox. Map every adapted object to the transaction, report, interface or batch job that calls it, and from there to a test case. The Custom Code (ATC) Remediation and Retest Tracker is set up for this, and it feeds the wider migration testing plan.

Before you sign off the custom code quality gate, ask for:

• ATC run ID, check variant and Simplification Database version, for both the ECC baseline and the converted system
• Findings by status (fixed, deleted, exempted), with zero open errors, or each one exempted with a named approver
• The deletion list, signed by the process owners, with the usage period it was based on
• A traceability link from each adapted object to an executed and passed test case
• The SRTCM results from the converted test system, with all findings resolved

Counts move between runs as content and code change, so explain the movement in the gate pack. To go deeper on scoping, remote ATC and adaptation, take the free Custom Code Migration: Scoping, Remote ATC and Adaptation course.

Frequently asked questions

Which ATC check variant should I use for S/4HANA 2025?

Use S4HANA_READINESS_2025, which SAP Note 3666462 brings into your central check system. It checks only the simplification items for 2025. S4HANA_READINESS_REMOTE checks everything in the Simplification Database and overstates your effort. If you target an earlier release, use the matching variant, such as S4HANA_READINESS_2023.

Can I run the S/4HANA checks directly in ECC?

No. The checks run in a central check system: S/4HANA 2025, the SAP BTP ABAP environment, or an AS ABAP 7.52 system. That system reads your ECC code over RFC through stubs that SAP Note 2270689 installs. ECC only needs the checked-system Notes and an RFC user with the authorizations in SAP Note 2672703.

Do RISE with SAP customers get the Custom Code Migration app?

Yes. SAP states that the app is part of every RISE with SAP subscription, running on the SAP BTP ABAP environment. It connects to your on-premise ECC system through Cloud Connector, and it supports usage-based scoping and deletion transports, which a 7.52 ATC system cannot do.

Is the custom code finished when ATC shows zero errors?

No. Zero errors means the code is compatible with S/4HANA structures, not that results are correct. You still need functional retests of every adapted object, runtime checks in SRTCM after conversion, and performance checks on heavy reports. Treat zero ATC errors as an entry criterion for testing, not an exit criterion.

Sources

1. Custom Code Migration Guide for SAP S/4HANA 2025 (2025.001), SAP SE (SAP Help Portal), 2026
2. Custom Code Migration Guide for SAP S/4HANA 2025 (2025.000), SAP SE (SAP Help Portal), 2025
3. Custom Code Migration Guide for SAP S/4HANA 2023, SAP SE (SAP Help Portal), 2023
4. Custom Code Migration Guide for SAP S/4HANA 1909, SAP SE (SAP Help Portal), 2019
5. Custom Code Migration Guide for SAP S/4HANA 1809, SAP SE (SAP Help Portal), 2019
6. Custom code adaptation for SAP S/4HANA: FAQ, SAP Community (SAP), updated 2026
7. Get started with the ABAP custom code migration process, SAP Community (SAP), updated August 2026
8. Remote Code Analysis in ATC: Technical Setup Step by Step, SAP Community (SAP)
9. S/4HANA Custom Code Impact Analysis Using ATC, SAP Community (member blog)
10. Automated custom code adaptation for SAP S/4HANA and SAP HANA on your SAP ECC system, SAP Community (SAP), October 2026
11. Custom code migration to SAP S/4HANA powered by SAP Joule for Developers, SAP Community (SAP), 2026
12. SAP S/4HANA Custom Code Migration Agent, SAP SE (SAP Help Portal), 2026
13. KBA 3794349: Central ATC remote analysis takes very long and shows RFC errors and bundle timeouts, SAP Support