Most of the enterprises running Mainframe applications written in languages like COBOL, PL/I are on a journey of modernization to make them maintainable and amenable to the more modular service-based programming paradigms. Such enterprises are looking for tools and techniques to help their developers understand the application faster and easier than what is possible through manual scanning of code. There is hardly any updated documentation for these legacy applications that have existed for 30-40 years. The comments in the code are not reliable as we were told by the clients, and the only reliable source of knowledge of the application is the actual source code. With key architects and SMEs retiring, the human knowledge of the applications is in decline. The scale of the applications and their interconnectedness is also challenging for SMEs to master. In such circumstances, the key challenge faced by any developer trying to maintain/modernize is how can they understand the application code to a level where they feel comfortable to refactor or rewrite. Use of automated tools become critical for understanding, decision making and scaling in such kind of modernization projects.