With a shortage of Cobol programming talent looming in the next decade and a clear need for greater software agility and lower operating costs, IT organizations have begun to make transition plans for mainframe applications. The trick lies in figuring out which applications to modernize, how to do it and where they should reside.

Applications fall into one of three groups based on scale, says Dale Vecchio, an analyst at Gartner Inc. Applications under 500 MIPS are migrating to distributed systems. "These guys, they want off," Vecchio says. As organizations begin peeling away smaller applications, they may move to a packaged application; port the application to Unix, Linux or Windows; or, in some cases, rewrite the applications to run in a .Net or Java environment, he says.

In the 1,000-MIPS-and-up arena, the mainframe is still the preferred platform. Applications between 500 and 1,000 MIPS fall into a gray area where the best alternative is less clear. An increasingly common strategy for these applications is to leave the Cobol in place while using a service-oriented architecture (SOA) to expose key interfaces that insulate developers from the code.

"If you expose those applications as a Web service, it's irrelevant what that application was written in," says Ian Archbell, vice president of product management at tool vendor Micro Focus International PLC in Rockville, Md. "SOA is just a set of interfaces, an abstraction."

"SOA at least allows you to break the dependency bonds," says Ron Schmelzer, an analyst at ZapThink LLC in Waltham, Mass.