ERP systems evolve in the post-implementation phase because of changing business requirements. Post implementation changes are likely to decrease the quality of ERP systems and of the data that they use, which negatively impacts organisational performance. We propose a framework for impact analysis of ERP post-implementation modifications. Our framework allows mapping dependencies among ERP system components and, based on these dependencies, automatically assessing the impact of a proposed change on both the design-time structure and run-time landscape of the system through a novel set of impact metrics. The framework also provides semi-automatic support to safely terminating the running process instances affected by change. The framework is evaluated with expert users in two pseudo-real ERP system implementations.