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Issues and Challenges Facing Legacy Systems

  • By Federico Zoufaly
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Maintaining and upgrading legacy systems is one of the most difficult challenges CIOs face today. Constant technological change often weakens the business value of legacy systems, which have been developed over the years through huge investments. CIOs struggle with the problem of modernizing these systems while keeping their functionality intact. Despite their obsolescence, legacy systems continue to provide a competitive advantage through supporting unique business processes and containing invaluable knowledge and historical data.

Despite the availability of more cost-effective technology, about 80% of IT systems are running on legacy platforms. International Data Corp. estimates that 200 billion lines of legacy code are still in use today on more than 10,000 large mainframe sites. The difficulty in accessing legacy applications is reflected in a December 2001 study by the Hurwitz Group that found only 10% of enterprises have fully integrated their most mission-critical business processes.

Driving the need for change is the cost versus the business value of legacy systems, which according to some industry polls represent as much as 85-90% of an IT budget for operation and maintenance. Monolithic legacy architectures are antitheses to modern distributed and layered architectures. Legacy systems execute business policies and decisions that are hardwired by rigid, predefined process flows, making integration with customer relationship management (CRM) software and Internet-based business applications torturous and sometimes impossible. In addition, IT departments find it increasingly difficult to hire developers qualified to work on applications written in languages no longer found in modern technologies.

Several options exist for modernizing legacy systems, defined as any monolithic information system that's too difficult and expensive to modify to meet new and constantly changing business requirements. Techniques range from quick fixes such as screen scraping and legacy wrapping to permanent, but more complex, solutions such as automated migration or replacing the system with a packaged product.

A Brief History

Debate on legacy modernization can be traced more than a decade, when reengineering experts argued whether it was best to migrate a large, mission-critical information system piecemeal or all at once.

Rewriting a legacy system from scratch can create a functionally equivalent information system based on modern software techniques and hardware. But the high risk of failure associated with any large software project lessens the chances of success. Researchers from the pioneering 1991 DARWIN project at the University of California, Berkeley, listed several factors working against the so-called "Cold Turkey" approach:

  • Management rarely approves a major expenditure if the only result is lower maintenance costs, instead of additional business functionality.
  • Development of such massive systems takes years, so unintended business processes will have to be added to keep pace with the changing business climate, increasing the risk of failure.
  • Documentation for the old system is frequently inadequate.
  • Like most large projects, the development process will take longer than planned, testing management's patience.
  • And finally, there's a tendency for large projects to end up costing much more than anticipated.

DARWIN advocated the incremental approach, popularly referred to as "Chicken Little," because it split a large project into manageable pieces. An organization could focus on reaching specific milestones throughout the long-term project, and management could see progress as each piece was deployed on the target system. Industry experts challenged this model several years later, saying the need for legacy and target systems to inter-operate via data gateways during the migration process added complexity to an already complex process. In addition, gateways were a significant technical challenge.

Many migration projects failed because of the lack of mature automated migration tools to ease the complexity and technical challenges. That started to change in the mid-1990s with the availability of tools from companies such as Anubex, ArtinSoft, FreeSoft, and Relativity Technologies. These tools not only convert legacy code into modern languages, but, in doing so, also provide access to an array of commercially available components that provide sophisticated functionality and reduce development costs. They help break up a legacy system's business knowledge into components accessible through modern industry-standard protocols, a component being a collection of objects that perform specific business services and have clearly defined application-programming interfaces (APIs).

Choosing A Modernization Approach

The Internet is often the driving force behind legacy modernization today. The Web can save an organization time and money by delivering to customers and partners business processes and information locked within a legacy system. The approach used in accessing back-office functionality will depend on how much of the system needs to be Internet-enabled.

Screen scrapers, often called "frontware," is an option when the intent is to deliver Web access on the current legacy platform. The non-intrusive tools add a graphical user interface to character-based mainframe and minicomputer applications. Screen scrapers run in the personal computer, which is used as a terminal to the mainframe or mini via 3270 or 5250 emulation. Popular screen scrapers include Star:Flashpoint, Mozart, and ESL. This technique provides Internet access to legacy applications without making any changes to the underlying platform. Because they're non-intrusive, screen scrapers can be deployed in days and sometimes hours. However, scalability can be an issue because most legacy systems cannot handle nearly as many users as modern Internet-based platforms.

Legacy wrapping is a second non-intrusive approach. The technique builds callable APIs around legacy transactions, providing an integration point with other systems. Wrapping does not provide a way to fundamentally change the hardwired structure of the legacy system, but it is often used as an integration method with Enterprise Application Integration (EAI) frameworks provided by companies such as SeeBeyond Technology, Tibco, Vitria, and WebMethods.

EAI moves away from rigid application-to-application connectivity to more loosely connected message- or event-based approaches. The middleware also includes data translation and transformation, rules- and content-based routing, and connectors (often called adapters) to packaged applications. Vendors generally offer one of three system-wide integration architectures: hub-and-spoke, publish and subscribe, or business process automation. XML-based EAI tools are considered the state-of-the-art of loosely coupled modern architectures.

EAI vendors advocate wrapping as a way to tap legacy data while avoiding the misery of trying to modify the underlying platform. This approach also enables integration vendors to focus on the communications and connectivity aspects of their solutions, while avoiding the complexity of legacy systems. Like screen scraping, wrapping techniques are applicable in situations where there's no need to change business functionality in the existing platform. However, none of the above approaches address the high cost associated with maintaining a legacy system or finding IT professionals willing to work on obsolete technology.

Another option is replacing an older information system with modern, packaged software and hardware from any one of a variety of ERP vendors, including Lawson Software, Manugistics, PeopleSoft, Oracle, and SAP. This approach makes sense when the code quality of the original system is so poor that it can't be reused. However, deploying a modern ERP system is not a panacea. An organization either has to customize the software or conform to its business processes. The first option is necessary if the original system was custom-made and provided a critical business advantage. Over the last couple of years, major ERP vendors have added tools to help adapt their applications to a customer's specific needs. However, customization still carries enormous risks that the system won't be able to duplicate a unique set of business processes.

In addition, a packaged system requires retraining of end users whose productivity will slow as they adjust to a new way of doing their jobs. IT staff also will need training on the new system. Finally, ERP applications carry hefty licensing fees that remain throughout the life of the software.

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This article was originally published on November 1, 2002

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