Migration of Legacy Information Systems
Authors: Stamati Teta , Kanellis Panagiotis , Stamati Konstantina , Martakos Drakoulis 
Published: October 2011

In recent years, the accelerated competition in the global marketplace rendered the corporate environment more volatile than ever. The businesses are heavily relying on technological advancements to deliver a vast array of initiatives across a variety of industries. The firms’ main partner in this increasingly complex and unpredictable journey is considered to be their information systems. Although the relevant industry offers an unprecedented rate of technological innovations, nevertheless there are cases where the information systems carry significant baggage from the past (Kelly, Gibson, Holland, & Light, 1999). There are aged systems that often form the central hub of the information flow within the organisation and are responsible for consolidating information about the business (Bisbal, Lawless, Wu, & Grimson, 1999; Sommerville, 2001) and thus they are called mission-critical legacy information systems. The term “Legacy”, according to the Oxford Dictionary, refers to any long-lasting effect of an event or process. The Legacy System describes an old system that remains in operation within an organisation. These systems often represent a massive, long-term business investment. Ulrich (1994) defined them as “stand-alone applications built during a prior era’s technology, but they are perhaps more widely understood as software systems whose plans and documentation are either poor or non-existent” (Connall & Burns, 1993). Bennett (1995) referred to the legacy systems as, “large software systems that we do not know how to cope with but that are vital to the organisation”, while Brodie and Stonebraker (1995) as “any information system that significantly resists modification and evolution to meet new and constantly changing business requirements”. Finally, O’Callaghan (1999), drawing on the characteristics of legacy systems, described them as “a large system delivering significant business value today from a substantial pre-investment in hardware and software that may be many years old. Characteristically, it will have a long maintenance tail. It is, therefore, by definition a successful system and is likely to be one that is, in its own terms, well engineered. It is a business critical system which has an architecture which makes it insufficiently flexible to meet the challenges of anticipated future change requirements.” Legacy systems as a subject area is often overlooked in favour of areas such as new technology developments and strategic planning of information technology. In this context, the following sections present an overview of the legacy information systems problems in terms of their scale and definition. The legacy system issues include the required man-effort and costs of maintaining and evolving existing systems and the current methods of migrating complex legacy systems to new technology. It is shown that legacy systems present a critical area of study in both software engineering and business information systems. Taking into account that the role of technology is not merely supportive but affects the way enterprises conduct their business, it is shown that it is outdated to consider the migration process as the simple replacement of aged or problematic hardware and software. Thus, the migration should be approached as a planned change process that first and foremost requires an understanding and a methodology that covers the range of issues and organisational entities involved.