Speaking Web Services: .NET and the Mainframe

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One of the quickest, easiest ways to expose mainframe data and applications is by using software that emulates a 3270-mainframe terminal and rolls mainframe data into robust HTML presentations or XML documents. One of the simplest variants is software that pulls data from the 3270 green screens and pops it into the browser, or transmits XML via HTTP. This approach is non-intrusive in that mainframers don’t need to be involved in development, and all the business rules the applications and data depend on are already embedded in the time-proven, reliable application. This approach can also deliver the quickest, most cost-effective payback as compared with new development.

Being able to publish the application as a Web Service lets one developer build the front-end of an application using Microsoft’s .NET, and another build a Java application to consume the same Web Service. A simple mainframe function becomes part of an emerging SOA, enabling the application to roll out across the enterprise.


Let’s examine several products that provide a simple approach to ramping up your existing applications for Internet data availability. Some argue it’s time to think about exposing your host applications and data using a completely different approach—one that affords more integration, albeit with greater development efforts and costs. Happily, a wave of host integration vendors, including IBM and Microsoft, are eager to oblige you. While this philosophy sounds great, the real truth is that, depending on your requirements, these terminal emulation products may well be a simple, effective solution. Sometimes, simple is best.

If the goal is to expose legacy data and applications, many vendors have introduced genuine host integration platforms—complete with support for both the J2EE and .NET environments—designed to complement their existing terminal emulation and Web-to-host products. For example:

  • NetManage markets OnWeb as a complement to its RUMBA terminal emulation package.
  • AttachmateWRQ sells MyEXTRA! as a complete host access/data integration/presentation package. The company also sells Verastream, along with its other terminal emulation products. (Note: At press time it was announced that the official merger between Attachmate and WRQ would take place over the next 60 to 90 days.)
  • IBM has an extensive set of terminal emulation, Web-to-host, and host integration products, including Host Access Transformation Services (HATS), which is heavily dependent on its WebSphere J2EE application server. (For that reason, NetManage, WRQ, and others stress the .NET-friendliness of their own offerings.)
  • The MAX tools from MAX Software enable the mainframer to easily point, click, and export legacy data (anything from editing, browsing, date-aging, scrambling, etc.) then transform it directly to XML. It’s not a “classic” Extract, Load and Transform (ETL) solution, but it does let the mainframer use a z/OS-, IMS-, and DB2-based utility to easily export legacy data (and reports) to XML.
  • SEAGULL recently announced they are acquiring SofTouch. And NEON, another big player, acquired ClientSoft.
  • Although technically not a terminal emulator vendor, illustro Systems uses a unique approach, as both z/WebHost and z/XML-Host run directly on either z/OS-OS/390 or z/VSE-VSE/ ESA. This eliminates the need and expense for additional platforms just to access your mainframe data. While both products support CICS, they also will work with any 3270-application environment, including IMS, Natural/ Adabas, even VTAM applications. Both products provide simple scripting facilities on the host side to automatically navigate through the applications to gather the required data and create customized result documents. This makes the client-side programming (e.g., .NET or Java) much easier because the XML document can be tailored to precise specifications.

Most users are looking for only one development environment, so if you’re a Microsoft shop, you’ll likely want to use Visual Studio .NET. Since .NET is a mobile-friendly application architecture, it’s actually a better choice for organizations that want to expose host applications and data to Personal Digital Assistants (PDAs), SmartPhones, and other wireless clients. Microsoft really hits a home run here because the .NET framework goes right down to those devices, through the Compact .NET framework that’s packaged with Visual Studio .NET. It’s easy to develop clients for those devices; the code and Graphical User Interfaces (GUIs) developed require minimal, if any, changes to work on mobile devices.


Many legacy applications were also developed using transaction monitoring and control systems such as IBM’s CICS. CICS transactions give developers a single entry point to execute a transaction that will be managed by the host but can participate in a broader transaction initiated by a controlling host, such as a .NET application. These methods let Web Services .NET and Java 2 Enterprise Edition (J2EE) developers reuse the legacy code and underlying data.

Often, applications weren’t written to use these facilities. But even here, designers can directly use the data stored on the host system, whether it’s stored in a database, such as DB2, or in flat file systems such as VSAM.

Consider security issues in this type of environment. Web Services application developers must consider the context in which their code is called. For example, will the system have to pass an individual’s security credentials through, or can the host system accept group credentials? How do you securely transfer credentials? How does the new .NET application connect to the host to begin with?

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