In a recent post, I talked about how BT, the UK telecom giant, has been in the process of shutting down hundreds of legacy systems as it moves deeper into SOA.
However, Michael Oara of Relativity, reacting to this report, advises that companies hold off a bit on wholesale dispensing of their legacy assets. There's still a lot of value in many systems that many modernized architectures may not be able to replace, he says: "I believe that the riskiest aspect of shutting down the application is the potential loss of some existing functionality that is still needed by the business. As an example, imagine that all screen interfaces were replaced by Web services. In such a case, is it possible that the application still receives some feed from an outside source? Even for the case of the user interface, how are we sure that all data elements and user actions are being replaced and nothing is lost? Furthermore, what about the application boundaries – could it be that we shut down something that does not properly belong to this application, or is shared with another application?"
Those are all great questions Michael raises. I ran across a great example in my own research for a recent piece in Insurance Networking News. Namely, The Hartford Insurance -- which leads the industry in SOA thinking and actions -- has some 30-40-year-old mainframe systems. However, while it is replacing those systems that serve commodity markets such as personal lines, it won't be throwing out the mainframes it uses for its high-value commercial lines anytime soon. Those mainframes are packed full of processes and logic that continue to porvide the company with competitive advantage.
Before thinking about throwing the switch on a legacy asset, Michael Oara advises performing "a careful and exhaustive analysis that would reveal (1) the application boundaries and (2) all application interfaces. Both these could be handled more or less automatically by a modern legacy analysis tool."
"A careful analysis can thus insure that no application input or output is left behind, as the user interface is replaced by Web services. Once the risk is eliminated, applications may be 'shut down' at a higher pace."
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