Converting Legacy Systems to Client-Server Apps


We usually refer to software or applications that run under old technology that remains in use while newer technology is available as a legacy system. Burke (2011) explained that legacy systems usually stay in place because of the cost required for the replacement, and also the efforts required for such replacement. In many cases the legacy systems are used because of the complexity of such system where time and efforts are required in understanding such system to be able to replace it with a new system and technology.   

Legacy Systems Conversion Process

Dossick and Kaiser (1996) explained that the motivations behind converting the legacy system to web browser platform application (Thin client) is to writ a single client for all platforms where one set of code will be maintained, and used by all the platforms. Another motivation that promotes such change is the fact that the modifications of such system will target specific situations or users, and converting legacy system to thin client will lower the training cost required, and will be easier for the user’s transition between applications.

It’s imperative that the legacy systems conversion decisions to be based on assessing the systems from two important points of view; the technical dimensions, and business dimension. The business dimensions will indicate the complexity of the business processes, while the technical dimensions will indicate the obsolescence of the legacy systems software and hardware platforms, the level of deterioration, decomposability and the maintainability of such frameworks (What-When-How, n.d.).

What-When-How (n.d.) explained that some of the steps required for the legacy systems conversion are the following:


  • Assessing the technical quality of the legacy system by considering the decomposability and obsolescence level of such systems. Through these processes, the decisions have to be made to perform business processes reengineering that can be aimed to take advantage of the Internet capabilities.
  • The decomposability of the legacy system will allow the legacy systems to be divided into major architectural layers, and also dividing such systems into Cooperating and independent business components.
  •  During the migration of legacy system’s information, it’s imperative to use the incremental approach (called Chicken Little) which eliminates the needs of accessing both the new database and the legacy during the migration process by introducing the gateways that can maintain the consistency of the data.
  • Using wrapping technologies to enable the coexistence of the newly developed components with the legacy functionality that can leverage the business functionality within the system until the conversion process is complete.

Legacy Conversion Problems

New software and hardware options represent challenges to many organizations that need to integrate their legacy systems with the new technology, and as such; even if such integration can work, it requires a huge effort and cost for the organization to develop and maintain the integration process. A good example for such difficulties is the fact that many mainframe systems are running with flat-files not a relational database, and integrating such system with a web interface will require a huge effort, and in many cases will add burdens to the new system’s dependability (Rea, 2011). In such case the organization has to build a web hosting system and front-end application to leverage their legacy mainframe data to the web.

Part of the problem with legacy system is that, it’s too expensive to operate and maintained, and also to keep the IT staff to work with legacy systems for a long time is a huge task for any organization where in most cases cost will be involved. It’s often a good option for many organizations to replace a legacy system with a proven package or in-house built systems that can meet the business requirements, and improve the business processes.

Good (2002) explained that legacy conversion is about extending and retaining the value of the legacy investment through the migration to new platforms. The legacy conversion process will reduce operational costs, and also add new capabilities to the new systems through the implementation for other technologies such as implementing web services.


Many organizations are continuing to use their aging systems to transact, process, transport, and communicate data to their customers. Part of the reason of having such system is the fact that such systems are very complex to be replaced, and the cost factor of replacing such system usually prevent such organizations from replacing these systems.

Burke (2011) explained that the support of legacy systems becomes very difficult as the technology changes create another hurdle for such systems to continue to work, and as such; organization are always looking to replace such system with more current technology and systems.

Finally, one of the problems that might represent challenges during the conversion of the legacy system to modern applications such as client/server platform (i.e. thin client or fat client) is the fact that these systems might be built with flat-files or record management services instead of a rational-database.


Burke, A. (2011) Definition of Legacy System [Online]. Available from: (Accessed: 16 June 2011).

Dossick, S. & Kaiser, G. (1996) WWW Access to Legacy Client/Server Applications [Online]. Available from: (Accessed: 16 June 2011).

Good, D. (2002) Legacy Transformation [Online]. Available from: (Accessed: 16 June 2011).

Rea, W. (2011) Problems with Legacy Systems [Online]. Available from: (Accessed: 16 June 2011).

What-When-How (n.d.) Migrating Legacy Systems to the Web [Online]. Available from: (Accessed: 16 June 2011).





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