For many German companies planning their SAP S/4HANA migration, the biggest fear isn’t cost or time. It’s operational disruption. And one of the most underestimated risk areas is the integration of external systems.
Most businesses operate a complex technology landscape built over years — with custom solutions, third-party platforms, industry tools and government portals. These systems are often deeply integrated with SAP and crucial for day-to-day operations.
At principal33, we work with organizations that can’t afford to lose any part of that ecosystem. We ensure that no critical external system is left behind, and that traceability and compliance are preserved throughout the migration.
What Are External Systems?
We define external systems as any application that interacts with SAP but exists outside the core ERP. Common examples include:
- Regulatory platforms (e.g. MaKo in German energy sector)
- Document management systems (DMS)
- Mobile apps for maintenance or field service
- Third-party CRMs (Salesforce, HubSpot)
- Industry-specific production or asset tools
- Finance or tax software (e.g. DATEV, FinanzOnline)
- Custom middleware or APIs
- Banking and compliance portals
In Germany especially, these systems are often required by law or mission-critical for audit trails and reporting.
What Can Go Wrong During a Migration?
Many of these interfaces were built for SAP ECC and rely on data structures, protocols or endpoints that no longer exist in SAP S/4HANA.
If the migration overlooks this, companies may face:
- Broken interfaces or failed data exchanges
- Business process disruptions
- Loss of traceability between systems
- Compliance issues or audit failures
- Parallel systems running in silos, increasing risk
How principal33 Handles Integration During Migration
We follow a tested methodology to ensure all external systems are integrated safely and reliably into the S/4HANA environment:
1. Inventory and categorization of all external systems
We assess:
- What systems connect to SAP and how
- Their technical protocols (IDOC, RFC, API, REST…)
- Their business criticality
- Ownership (internal, third-party, public)
2. Compatibility check with S/4HANA
We review:
- Which integrations require updates or replacement
- Whether existing middleware is compatible
- Changes in SAP APIs or data structures
- Any version/licensing issues from third-party providers
3. Integration plan with sandbox testing
We create a dedicated plan that includes:
- Technical redesign or configuration of interfaces
- Simulated data transfers in a safe environment
- Functional validation with business users
- End-to-end traceability testing
- Rollback or fallback strategies for go-live
4. Phased go-live based on business priority
Rather than migrating all integrations at once, we sequence integrations based on functional go-lives, such as starting with Finance or Procurement.
Common Scenarios from German Projects
In German client projects, we often handle integrations like:
- MaKo platforms for energy providers
- Asset management and SCADA systems in manufacturing
- Government-required e-invoicing portals
- Tax software like DATEV or FinanzOnline
- Shop-floor production tools linked to SAP PP/PM
In all cases, a loss of connection results not just in technical issues — but regulatory, financial, or reputational risk.
5 Key Recommendations
- Don’t treat external systems as secondary — they are critical.
- Involve third-party vendors early — don’t assume they’re ready.
- Test with real data and full load, not just mock cases.
- Document every interface and establish ownership for each one.
- Ensure full traceability and auditability — especially in regulated sectors.
Conclusion
Migrating to SAP S/4HANA isn’t just about SAP. It’s about preserving the entire digital ecosystem that supports your business.
If external systems fail during the transition, compliance, continuity, and operational trust are at risk.
At principal33, we help you migrate without losing anything essential. We design tailored integration strategies focused on stability, traceability, and business continuity — especially for complex German landscapes.
Ready to move to S/4HANA without disconnecting from what matters? Let’s plan it properly.
