Clean Core on-prem, pratical meaning

[patrick_weber11]

Hi all,

we're running S/4 HANA 2023 FP1 on-prem. We came from ECC system by brownfield approach. This means, we simply migrated our 20+yrs development Z-objects over.

Now I want to clean up this mess and become more clean core compliant. To be honest, we can't be even more far away from clean core compliant. Also there are currently no plans to move to any cloud scenario. But at least I want to be prepared.

I read through lots of blogs, Devtoberfest and TechEd and now have a good feeling of what clean core means. Now I try to analyze our clean core index struggling with what it means.

What is clear to me is:
- get rid of user exists (~130)
- get rid of modifications (~850)
- get rid of SAPScript (~50)
- get rid of implicit enhancements.

What about all the other objects? 
- DDIC domains, data elements tables
- BTE events
- function modules (several hundret)
- Z-report and includes (~2000)
- SQ01/SQ02
- copy rules (SD), which are some kind of modification
- alreads implemented BAdI

We will not become 100% clean core compliant but I want to get as close as possible. Especially all these Z-reports drives me crazy. What does clean core means for these? Do I need to replace all of them by custom API and new UI to become compliant? We still use only few Fiori Apps and most users and processes stick to SAP GUI.

Do I need to supersed each funciton module with an API?
In SD there are many modifications like copy rules or condition rules. How to replace these?

How to handle all BAdI implementations already done? They're not visible in "Custom Code and Logic" App and I don't think it makes sense to re-implement them there?

Which other objects do I need to take into account? As a first indicator, I try to change ABAP language and found that several objects (like reports or FM) doesn't support this. Is this a valid approach?

Greets from the beginning of a long journey
BR Patrick

[sujith_sulochana]

Hi Patrick,

I just want to share my thoughts with you on this topic. The enhancement what you have mentioned is just only a branch of bigger spectrum of clean core. In your case as it is brown field implementation the migration to clean core can happen only gradually . As per me ,this would be a good approach. The biggest challenge is the non availability of SAP released objects for all scenario's whether it is enhancements or api. My recommending are given below

1. Gradually migrate users to stand fiori apps instead of gui transactions

2. For all new enhancements choose cloud first approach 

3.Follow 3-Tier approach proposed by sap for enhancement.

What about all the other objects? 
- DDIC domains, data elements tables—> Depends on case to case on how to migrate to clean core. But these objects custom object are allowed in clean core.  

- BTE events—> not supported in clean core. 
- function modules (several hundret)—> One option is to look for standard class methods. For instance's ,cloud class method is available to replace FM 

MD_CONVERT_MATERIAL_UNIT

- Z-report and includes (~2000)—> Not supported in clean core. Evaluate each program on how to migrate to clean core.
- SQ01/SQ02–> Use fiori app view browser

for the below two enhancements look for released BADI’s . If there is not standard release BADI’s stay in tier3. 
- copy rules (SD), which are some kind of modification
- alreads implemented BAdI

The above mentioned points are based on my self learning on clean core. If you disagree or has different view points on my suggestions the please post here.

Thanks,

Sujith

[patrick_weber11]

Hello Sujith, thanks for your input and I agree with you that development is just one part of Clean Core. For me the most relevant as I'm responsible for this in the company I'm working. Your answer confirms most of my ideas of our clean core journey. One thing I'm still missing is, how to handle Z-function modules? I don't care about standard FM and their successors but we also use hundrets of Z-function modules. Probably we can't replace all of them with an API. Do you know, if these are clean core compliant or must also be replaced? Clean core will be a journey of several years for us but at least we have to start at some point. First of all, I defined our clean core index to get a better feeling of where we are now. Next we defined new development guidelines to stop classic development and use cloud-first approach whereever possible. During next year, we will evaluate all user-exists and modifications and checks, if they're still needed and how to solve it alternatively. We're on year 2 on S/4 HANA and I recognize, first business colleagues starts to ask for Fiori instead Z-TCode. I hope they will become more.

[sujith_sulochana]

Hi Patrick,

[sujith_sulochana]

As per my understanding custom function modules are still supported in abap cloud. You need to perform could readiness check on them and fix the findings.