SAP’s “clean core” guidance is simple: keep S/4HANA as close to standard as possible. The less custom ABAP you have, the easier your upgrades, the lower your risk, and the smaller your maintenance burden.
But most organizations didn’t customize SAP for fun. They did it because the business needed processes that standard SAP didn’t support. The real question isn’t whether to keep SAP clean — it’s where to put the business-specific processes that drove the customization in the first place.
Here are nine processes that organizations commonly build inside SAP with custom ABAP. Every one of them creates technical debt that blocks upgrades. And every one of them is a better fit for an external workflow orchestration layer.
Multi-Tier Procurement Approvals
In SAP:
Custom workflow templates, BAdIs, and decision tables to route approvals based on cost center, amount thresholds, and org hierarchy.
Outside SAP:
A configurable workflow with conditional routing that writes approved POs back to SAP via standard BAPI. Change the approval chain in minutes, not sprints.
Employee Self-Service Portals
In SAP:
Fiori customization or legacy WebDynpro apps for leave requests, address changes, benefits enrollment, and pay stub access.
Outside SAP:
A modern, branded experience backed by standard SAP HCM APIs. Users get a better interface. SAP stays untouched.
New Hire Onboarding
In SAP:
Heavy custom middleware to orchestrate across SAP HCM, Active Directory, facilities, IT equipment, and training (LMS).
Outside SAP:
A single workflow that spans all five systems. SAP is one endpoint — not the orchestrator.
Invoice & Payment Exceptions
In SAP:
Custom ABAP exception handlers for three-way match failures, blocked invoices, and payment run exceptions. Among the hardest custom programs to migrate.
Outside SAP:
The routing and resolution workflow lives externally. Results write back to SAP.
Vendor & Partner Portals
In SAP:
Custom Fiori apps or legacy portal technology to give third parties access to PO acknowledgment, ASN submission, and payment status.
Outside SAP:
A purpose-built portal connecting to SAP through standard OData services. Partners never touch SAP directly.
Capital Project Requests
In SAP:
Custom PS/IM workflows for business case submission, multi-department approval, budget checks, and asset creation.
Outside SAP:
A single orchestrated process calling SAP for financial checks and asset creation via standard APIs.
Audit & Compliance Checklists
In SAP:
Custom ABAP for SOX controls, segregation of duties reviews, and periodic access certifications.
Outside SAP:
Forms and workflows updated by compliance teams without ABAP developers. Audit trails captured in the orchestration layer.
Plant Maintenance & Inspections
In SAP:
Significant Fiori customization for mobile work orders, inspection checklists, parts requests, and photo capture.
Outside SAP:
Field-friendly interfaces feeding results back into SAP PM through standard interfaces.
Custom Data Entry & Reporting
In SAP:
Z-transactions and custom ALV reports built for every data entry and reporting need that standard SAP doesn’t cover.
Outside SAP:
Dynamic forms that collect inputs, validate against SAP master data via OData, and write results back or generate reports — without a single line of ABAP.
The pattern
Every one of these processes touches SAP data. But none of them need to live inside SAP. The data stays in SAP. The experience, logic, and orchestration move out. SAP becomes a system of record, not a system of engagement.
The Clean Core, Made Practical
Not by removing the processes the business needs — but by building them in the right place. Move the customization layer outside of SAP and the upgrade problem disappears.
For the full breakdown of this approach — including how to run ECC and S/4HANA in parallel during migration — read The Customization Layer for SAP. For the six challenges that drive these customizations in the first place, see 6 Challenges That Stall Every S/4HANA Migration.
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