From Custom Code Inventory to Clean Core: CORE-Fit—A Portfolio-Level Methodology for Rationalizing ERP Extensions in SAP S/4HANA

Abhinav Jain (Independent Researcher, Pennsylvania, USA)

The Eastasouth Journal of Information System and Computer Science
Vol. 3 No. 01 (2025): The Eastasouth Journal of Information System and Computer Science (ESISCS)

Enterprise resource planning (ERP) modernization increasingly requires organizations to reconcile two competing objectives: preserving business-specific capabilities and reducing the lifecycle burden created by tightly coupled custom code. Clean Core addresses this tension through fit-to-standard processes, governed extensibility, stable interfaces, and deliberate placement of capabilities inside or outside the transactional ERP core. This paper introduces CORE-Fit (Customization Optimization, Rationalization, and Extensibility Fit), a design-science methodology proposed in this study for rationalizing inherited ERP customizations into five disposition paths: retire or standardize, key-user extension, on-stack developer extension, side-by-side extension, or governed exception and remediation. The underlying principles and related SAP approaches to custom-code rationalization and extension design were already established; CORE-Fit does not claim novelty for retirement, fit-to-standard, or extension technology selection as individual concepts. Its contribution is the specific six-stage portfolio-level decision artifact that integrates business-need validation, standard-fit analysis, transaction and data proximity, lifecycle independence, integration and economic/operational fit, and governance into five explicit disposition outcomes. CORE-Fit is evaluated using an anonymized customer-system assessment of 121 RICEF objects. The resulting disposition comprised 22 objects (18.2%) retired or standardized, 11 (9.1%) classified as key-user extensions, 73 (60.3%) as on-stack developer extensions, 15 (12.4%) as side-by-side extensions, and none as governed exceptions. The results illustrate that Clean Core rationalization need not equate to aggressive externalization: in this portfolio, most surviving requirements remained close to the transactional core through governed developer extensibility. The study presents a case-evaluated methodology for applying these criteria consistently across a legacy customization portfolio.