Clean core and side-by-side extension
SAP's clean core principle asks customers to keep the ERP close to standard and put custom logic elsewhere. In practice that means using released APIs, in-app extensibility and SAP Business Technology Platform instead of modifying standard objects. Upgrades become smaller events, and custom code is easier to test and retire. Standard behavior is also better documented and supported by SAP.
We help classify existing custom ABAP into keep, rebuild, replace or delete, using usage data and code analysis rather than assumption. Many Z-programs are unused, and removing them before migration shrinks cost and risk considerably. Side-by-side apps typically run on SAP Business Technology Platform with the Cloud Application Programming model, calling released APIs and receiving business events. They can be built, tested and released independently, so a change to a sales approval screen no longer waits for an ERP transport window or risks affecting finance postings.