In this paper, we propose a new method to support the maintenance of large-scale business application systems, and discuss its implementation. Large-scale business applications handle huge numbers of data items. To improve the maintenance of business application systems, our method proposes integrating the following features: (1) a high-level control-flow diagram which displays an unstructured program in a structured form, (2) a data dependency diagram which is essential in understanding business rules, and (3) ripple effect analysis functions to find the side effects of program modification. This paper also describes an execution path model and a repository which enable us to efficiently implement the above features. The system has been developed to reflect the discussions with software maintainers.