Due for an Inspection? Why illegal ‘SAP Tuning’ blocks your upgrades (The harsh Clean Core reality)

Let's be clear from the start: custom code is not the enemy. In some cases it's exactly what sets a company apart - a genuine competitive advantage that no standard process could deliver. That kind of code deserves to be protected and carried forward.

The problem is that, in most systems, this differentiating code is the exception. The vast majority is something else entirely: undocumented, unused, and quietly working against you. This article is about telling the two apart - and being honest about how much of your "business-critical" tuning really earns that label.

Imagine your enterprise ERP is an expensive, extremely high-performance premium sports car. But over the last few years, you, your IT department, and various external consultants have been busily modifying it in the garage: An unapproved rear spoiler was bolted on, the exhaust manipulated, the emissions sensors bypassed, and the suspension lowered.

On a private country road, this bespoke ‘custom tuning’ might be really fun. The car drives exactly the way the driver (the business unit) wants it to in that moment. But then the moment of truth inevitably arrives: The official vehicle inspection is due.

The inspector just shakes his head in disbelief. The massive rear spoiler restricts the legally required rearward visibility. The lowered suspension loses control on the standardized brake tester. The manipulated emissions are off the charts. The consequence is harsh but unavoidable: Your car loses its operating license on the spot.

It gets even more dramatic when the car manufacturer tries to push a critical over-the-air software update overnight to patch a highly dangerous security vulnerability in the engine control unit. The update aborts immediately because your manipulated exhaust sensors can't process the manufacturer's new, standardized values. It’s a similar story if your modifications prevent a safety-related recall by the manufacturer.

Welcome to the dangerous reality of highly customized SAP systems.

What illegal backyard tuning is in the automotive world, the historically overgrown Z-code (custom code) is in the SAP world. Modifications to SAP standard tables and programs, deep system interventions, wild interfaces, and hard-coded values that were declared ‘urgently business-critical’ in a project years ago are today one of the most massive blockers to innovation, security, and stability.

With S/4HANA, and especially with the move toward the cloud, SAP is forcing a hard, uncompromising paradigm shift: the Clean Core.

The strategic message from Walldorf is unmistakable: Consistently use standard processes. Minimize your own customized code. Only extend the system via officially released APIs and state-of-the-art cloud extension technologies like the SAP BTP. Anyone who doesn't play by these new rules effectively loses their upgrade capability – and thus their ability to innovate – and maneuvers themselves into a technological dead end.

The crushing technical debt: Why tuning becomes the ultimate showstopper

Many IT departments and CIOs underestimate the technical risks of an ‘unclean’ migration. If we do not clean up the system's core before the transition, we carry a  massive overload straight into the new S/4HANA world. The dangers wait primarily in two areas:

• The custom code jungle (The manipulated suspension): In almost every older SAP system, there are hundreds of thousands of lines of ABAP code written over the years by constantly changing developers and service providers. Often without clean documentation, without encapsulation, and with deep interventions in SAP standard objects. During the next S/4HANA release upgrade, SAP might change exactly these objects. The result? The old custom code stops immediately or delivers incorrect results. In the worst-case scenario, the system comes to a standstill. In each and every case the maintenance alone of those outdated modifications consumes massive amounts of time, budget, and testing resource

• The overgrown integration landscape (The poorly engineered trailer hitch): Interfaces to third-party systems, logistics providers, or web shops were often built ‘quick and dirty’ in the past. There is often no clean API governance; old protocols are used. Now, if SAP updates its core architecture and shuts down old interface technologies, these unofficial connections break without replacement. Data is irretrievably lost, and business-critical external systems lead nowhere.

The incorruptible inspection report for your SAP system: ATC and Integration Mapping

To successfully navigate the rocky road to the Clean Core, pure expert gut feeling or a glance at outdated architecture diagrams is not enough. You need hard, incorruptible diagnostic logs straight from the engine room.

In the SAP world, the primary tool for this is the ABAP Test Cockpit (ATC). The ATC results are exactly what the detailed defect report is at the vehicle inspection. They relentlessly reveal at the code-line level which Z-code is no longer S/4HANA-compatible, which obsolete functions are being used, and where hard modifications violate the SAP standard.

But in today’s networked world, purely isolated observations of code lines are no longer enough. A future-proof system must be analyzed holistically. The integration of third-party systems and the evaluation of complex interface architectures are just as business-critical as the code itself. If a faulty interface paralyzes your logistics, even the cleanest ABAP code in the core won't help you.

Keep, Drop, or Renovate: The strategic roadmap to the Clean Core

To make your digital sports car permanently roadworthy again and prepare it for the cloud, you have to make decisions of strategic importance. You must determine which tuning parts can stay, which need to be rebuilt, and which must be ruthlessly thrown into the scrapyard. For all your custom code and integrations, this means:

• Drop (Scrap): Code, transactions, and interfaces that have demonstrably not been used productively for over a year are rigorously deleted without nostalgia. In our project practice, this shockingly accounts for around 80% of historical legacy burdens! It makes no sense to migrate code to S/4HANA that nobody uses anyway.

• Renovate (Retrofit): Z-code that remains absolutely business-critical or has become a competitive advantage should be contained. It should be rewritten and refactored so that it complies with strict Clean Core principles. Specifically, this means outsourcing complex logic as ‘Side-by-Side Extensibility’ on the SAP Business Technology Platform (BTP) or using ‘In-App Key User Extensibility’ and 'Developer Extensibility' directly in the system.

• Keep (Retain): Official, released extensions that fully comply with the new S/4HANA standard and strict cloud guidelines are allowed to stay.

The path to the Clean Core is not SAP harassing or punishing you. It is the one of the most critical investment in the survivability and agility of your IT landscape. Only a clean, standardized core enables you to keep up with future innovation cycles, AI features, and security updates (just like the saving OTA update for the car) in real time and without months of million-dollar testing phases.

How would your current SAP system perform today in a ruthless, technical ‘vehicle inspection’ – and would you get the inspection sticker for S/4HANA? 🤔

(To give you exactly this ruthless transparency, IBIS Prof. Thome utilizes state-of-the-art analyses in its ‘Transform’ solution suite. We evaluate your ATC results, translate your integration architectures into tangible dashboards, assess all technological objects – not just ABAP-based ones – regarding their Clean Core Level, and – as a crucial value-add – map these technical defects directly to the actual system usage of your users where possible. In doing so, we provide you with a watertight, data-driven factual basis for your multi-million dollar ‘Keep, Drop, or Renovate’ decisions. So that your core gets clean – and stays that way.)

The featured image was generated using AI.