A ROAD MAP FOR MIGRATING LEGACY SYSTEMS TO CLIENT-SERVER

Applications developed during the 1970s in a centralized computing environment have become legacy applications in today's decentralized world, increasingly expensive to maintain. One way to improve their use and maintainability in the present environment is to migrate them to the client/server (C/S) world while salvaging as much as possible during that process. This paper, a road map for that migration, examines how legacy applications differ from C/S applications and prescribes a course of action to remove the non-C/S characteristics from legacy applications and to replace them with C/S characteristics. In this process we need to address a variety of technical issues involving databases, network and configuration management as well as organizational issues such as data and process models used by different parts of the organization, and user/customer training in the new C/S paradigm. The goal of the migration process is to implement an application environment consisting of heterogeneous, distrubuted, multi-DBMS applications dynamically linking legacy systems and relational or object-oriented databases in real time, without the coding costs or challenges of two-phase commit. Middleware tools are used widely to re-engineer legacy applications to fit a C/S environment. A variety of CASE tools are available to support modifying such functions as query and reporting, and cross-platform development. The paper discusses these issues and concludes with a brief description of resources and tools that can help in travelling the migration road.