Insights into Custom Code Adaptation: From SAP ECC to S/4Hana

The Strategic Role of Custom Code in S/4HANA Projects

The migration from SAP ECC to SAP S/4HANA is one of the most significant transitions many organizations will undertake in the coming years. Beyond the technical upgrade, it is a shift in how systems operate, integrate, and support business processes.

S/4HANA’s architecture, with its in-memory database, simplified data structures, and redesigned functionalities, offers opportunities for improved performance and streamlined operations. Yet, it also requires organizations to critically assess and adapt one of the most deeply embedded elements in their ECC systems: custom code.

Over time, custom developments have been created to meet specific operational requirements. These adjustments, while business-critical in ECC, often do not align directly with the S/4HANA data model or technical standards. Addressing this gap is essential to ensure both stability and long-term maintainability in the new environment.

Key Challenges in Custom Code Adaptation

Several aspects of the S/4HANA architecture have a direct impact on existing developments:

Data Model Changes: Many traditional ECC tables have been replaced or consolidated, most notably in Finance with the Universal Journal (ACDOCA).
Functional Simplification: Some transactions and processes have been re-engineered or removed, requiring alternative approaches in custom code.

Programming Paradigm Shifts: While ABAP remains the backbone, S/4HANA leverages techniques such as Core Data Services (CDS) and ABAP Managed Database Procedures (AMDP) to fully exploit HANA’s capabilities.

Business Partner Model: The unification of customer and vendor master data under the Business Partner object necessitates significant adjustments to any custom developments interacting with these datasets.
These are not minor adjustments. They require a structured analysis to determine which custom objects should be retained, adapted, or retired.

A Structured Approach to Adaptation

From a technical perspective, successful adaptation involves several phases:

Assessment of Existing Code

• Identify all custom objects in the ECC system.
• Determine their actual usage to avoid unnecessary adaptation of inactive code.

Impact Analysis

• Use tools such as SAP’s ABAP Test Cockpit (ATC) and the Custom Code Migration App resp the Custom Code Adaptation Toolset ® by Lupus Consulting to identify incompatibilities.
• Map dependencies and interactions between custom code and standard SAP functionality.

Adaptation Strategy

• Prioritize business-critical functionality.
• Plan for code retirement where functionality is replaced by standard S/4HANA processes.
• Align adaptation efforts with long-term architectural goals.

Execution and Optimization

• Apply necessary syntax and structural changes.
• Optimize for HANA performance by leveraging modern ABAP constructs.
• Ensure integration with new frameworks, particularly the Business Partner model.

Validation and Testing

• Perform targeted testing to confirm functionality and performance.
• Involve business users early to validate outcomes against operational needs.

Lessons Learned from Practice

Experience shows that early attention to custom code adaptation reduces project delays and post-migration issues. Some key observations:

• Not all custom code is worth migrating: Many organizations discover that a significant portion of their developments are no longer used.
• Business Partner adaptation is often underestimated: The integration of customer and vendor data into a single model requires more than simple technical changes; it affects reporting, interfaces, and master data processes.
• Performance opportunities exist: Reworking legacy code to align with HANA’s strengths can deliver measurable improvements beyond compliance.

Expert Commentary: Lupus Consulting’s Perspective

From our experience in large-scale S/4HANA migrations, the most successful projects treat custom code adaptation as a strategic exercise, not just a technical necessity.

Three factors consistently make the difference:

1. Prioritization Based on Business Value: Adapting every line of code is inefficient. A targeted approach ensures that only relevant, high-impact developments are carried forward.
2. Early Business Partner Integration: Addressing BP-related code changes early avoids downstream disruptions in master data processes.
3. Alignment with Future Architecture: Migration is the right time to modernize developments using CDS views, AMDP, and other HANA-optimized techniques.

A well-planned adaptation process not only ensures a stable go-live but also positions the system for long-term performance and flexibility. In this way, custom code adaptation becomes an enabler of innovation rather than a migration hurdle.