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Legacy Systems and SOA Legacy Modernization Legacy modernization is a significant aspect of an enterprise's adoption of SOA. Any enterprise with an IT presence during the past few decades is bound to have legacy applications that assist in running its business. Legacy systems can exist at the infrastructure level, as well as at the operational level; for instance, an IBM CICS® mainframe running an enterprise human resources system. Legacy systems can also exist as either outdated or poorly written software applications that run on specific infrastructure components and operational environments. When an enterprise takes the initiative to modernize its IT infrastructure and align it with business requirements, the IT team must take a closer look at existing legacy systems before building a business case for the transition to an SOA-based portfolio. Such analyses are frequently performed in silos, meaning specific isolated business domains are chosen for impromptu legacy modernization. If legacy modernization is performed without taking a holistic enterprise wide view or without the context of the dependent and related business domains or competencies, it opens the potential for creating duplicate services and application program interfaces (APIs). The duplication arises from a lack of detailed analyses of the existing service portfolio. Existing services must be carefully analyzed using an 80-20 rule: If an existing service satisfies at least 80 percent of the required capability of a current modernization requirement with only a 20 percent effort required to create it from scratch, then it is advisable to realize the new requirement by building around or on top of the existing service. If the enterprise IT organization's method of operation is through the initiation of silo SOA legacy modernization efforts, the potential gains of SOA may be compromised. That is, if the modernization takes place without evaluating the entire system, chances are it will not result in attainment of an authentic SOA. In these kinds of business models, SOA is not a good approach to undertake. When all is said and done, the business value of SOA would be hard to justify to business stakeholders. Understanding the Technical Limitations of Legacy Systems A significant number of SOA efforts depend heavily on existing data and applications that reside in legacy systems. Certain features of legacy systems are often not a natural fit with the real-time nature of SOA-based applications. A classic example of this mismatch is a single-threaded legacy application, where a business function is implemented for only single-threaded access. Another example of legacy system limitations is the case of scheduled batch processes, which only run at fixed times. Today's competitive enterprise demands more real-time transaction requirements. When deciding to make legacy applications or data become part of an SOA system, it is imperative to understand the limitations this can place on the overall SOA. The single-threaded nature of this particular legacy application, is an example of a technical limitation of a legacy system. Business capabilities of the modern enterprise often warrant transactional capabilities from the infrastructure that are beyond the capabilities of the existing legacy system. In such cases, an approach may be to gradually phase out the legacy system by building SOA-based solutions that are built on a modern infrastructure portfolio. To do this, the organization needs to select the most business-critical functions and replace their existing legacy implementations with a solution based on a technologically modern infrastructure. This phase can then be followed by the modernization of the remaining business functions. Such an approach provides a viable option for a phased sun-setting of the legacy system. QAT’s approach to SOA is founded on our practical experience in building working products and solutions for enterprises across the globe. We help enterprises make the right business and technology decisions. For more information, please visit http://www.qat.com/es_soa_overview.asp and http://www.qat.com/ms_legacy.asp. |
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