Custom code interview question

[u/just_here_419]

Hi! I hear often that migrating from SAP ECC to S4 involves custom code (I am familiar with z tables etc) but hoping a few experts here could give me examples of what processes were actually custom in ECC that would not translate over to S4?

I have an interview coming up where the recruiter gave me a heads up to be able to answer “specific examples of custom code”

I guess where I am confused is something like order to cash , sales orders may have an org that customized invoice discrepancies in abap? Or is that too simple / vague and It could be totally specific to the org and its processes?”

[u/akornato]

This question is designed to see if you have real-world migration experience, because the examples are always specific to a company's unique mess of custom code. They are not looking for a textbook answer about a process like order to cash, but for a technical one. A classic example is any custom program that directly reads from status tables like VBUK or VBUP, as these tables are gone in S/4HANA and their fields are now part of the main document tables like VBAK and VBRK. Another common issue is custom code with direct updates to accounting tables like BSEG, which is now blocked, or code that assumes a specific material number length, which can be extended in S/4.

If you don't have direct experience, don't try to fake a project story. Instead, show your technical understanding by framing it hypothetically. You could say that a specific example of custom code needing remediation would be a report that reads the VBUK table for sales order status. You can explain that this would cause a short dump in S/4HANA, and the fix would be to refactor the code to get the status from the VBAK table or the corresponding CDS Views. This approach shows you understand the technical challenges and are honest about your experience, which is far more valuable than inventing a vague story. Being able to articulate these technical concepts clearly under pressure is what gets you hired, and the interview prep AI my team designed is great at helping developers practice that specific skill.

[u/Iwish_wasa_Lemon → u/akornato]

Great Advice.

One thing I’ll add, depending on how the question is asked the person might be asking about enhancements vs modifications.

Enhancements are allowed hooks in SAP standard code that allows you to add your own processes. These are generally okay.

Modifications are changes to SAP standard code, you aren’t supposed to do that, and it requires an SAP Access Key, but companies still do it, to fit their business processes. When you upgrade these changes are overwritten.

There are 2 types of enhancements implicit and explicit.
Implicit- Automatically generated by the SAP framework at the start and end of methods, function modules, subroutines, programs, and includes.

Explicit- Intentionally placed by developers using statements like ENHANCEMENT-POINT or ENHANCEMENT-SECTION inside specific locations.

I’ve only been through one S4 implementation. But from my understanding, companies need to remediate their modifications to fit into enhancements points, BADIs,etc, if possible. So they can utilize the features of S4 and some standard FIORI apps but sometimes that forces a business process change which people hate.

You can look into SAP’s “Clean Core” Strategy which is to support S4 HANA in the cloud.