In the IT shops where the Mainframe is still in operation, you can find millions of lines of legacy code. For instance, COBOL, PLI, Natural, and PowerBuilder are the main contributors.

Consequently, some users now run their applications online in dialog mode, while others run them in batch mode as background jobs. In addition, these users now plan to migrate to a service-oriented architecture and use the mainframe as a hub, where client business units can access a wide assortment of Web services to build into their new business processes.

However, high migration costs prevent them from doing so. In particular, the highest costs lie in developing Web services from scratch or adapting those available on the market.

Key reasons to go for re-engineering.

• First, to become faster and more flexible in responding to user requirements
• Second, to give the users a wide range of ready-made services
• Third, to unify common business functionality
• Finally, to cut the costs of maintaining an oversized software base.

4 Ways to re-engineer Legacy Apps.

• First, one option is to purchase a standard set of Web services from a software vendor and to adapt their business processes to them. This requires them to give up much of their local rules and specific business logic. Nevertheless, they can customize the overall processes, but they still have to accept the detailed data and algorithms provided by the vendor.
• Second, a user can obtain Web services from the open source community and then modify them to fit his needs. This gives him the possibility of inserting his own rules and detailed logic; however, it requires him to have specialists who can work with the open source. If such specialists are not available, this approach can therefore become very expensive depending on the degree of change.
• Third, a user has the option to develop his own Web services. To do that, the user must first start with an analysis of his requirements and identify each and every Web service he will need in his planned business processes. Once he has identified them, he can then begin to develop them, for instance, by an agile development process.
• Fourth, a further option is to reuse the existing legacy systems or, at least, parts of them as the building stones of the new SOA architecture. The advantage of this approach is that it is generally quicker and cheaper. In fact, the wrapping of a module typically requires no more than one person-day.