Mainframes' new tricks

If you want to keep data and applications on your mainframe but extend them enterprisewide, consider four options.

* Screen scraping or enhanced terminal emulation. In these options, a Web site acts as a terminal emulator, intercepting data intended for display on a mainframe terminal, and presents it on a non-mainframe system. However, a standard terminal emulator has a number of advantages. For one, systems administrators do not need to install software on the client PC. Secondly, the display can be much more attractive and readable than the standard text-based, green screen. And finally, on-screen buttons and other navigational tools can replace awkward function keys. Stephen Laich, a senior systems developer at Pinnacle Decision Systems Inc., a consulting and software development company, deems screen scraping "inexpensive, very fast and very tactical." In fact, some organizations have set up basic screen-scraping systems in a day or two.

* Wrapping. In this method, a server-based system is used as a front end to the mainframe. Users coming to a Web site use the front-end system to enter data, for example. The front-end system saves the data in a relational database. Periodically, the data is pulled from the relational database and sent to the mainframe. Unlike screen scraping, this approach allows developers to completely re-engineer the interface to the mainframe. But, on the downside, it takes more time and a higher skill set to develop than a screen-scraping solution. A second disadvantage according to Laich, is that because wrapping acts as a buffer to the mainframe, users can't get complex, real-time data.

* Middleware solutions. In contrast to the store-and-forward methodology of wrapping, middleware provides direct programmatic access to legacy codes and processes. "To use middleware, you typically introduce a server or middleware system that knows how to talk to the operating environment of the legacy system," Laich said. But he adds that middleware is more complex than either screen scraping or wrapping. It can also be expensive. A dedicated server needs to be configured with special host integration software.

* Enterprise application integration. These applications, from vendors such as PeopleSoft Inc. or SAP America Inc., combine middleware, as in option three, with extra functionality. For example, PeopleSoft includes accounts receivable, accounts payable and billing; SAP has these plus manufacturing functions. These products are expensive and can take many months to implement.

"Think of the four options as increasing in complexity, requiring more resources and time to implement, but also as providing tighter integration to the mainframe," Laich said.