Microsoft recently released Host Integration Server (HIS) 2004, a major update to its IBM mainframe integration server that adds important new features and enhancements. Unlike most Microsoft interoperability products, which are typically designed with more of an eye toward migration than true integration, HIS 2004 will actually help customers get more value from their existing legacy platforms—in this case, IBM mainframes and iSeries (formerly AS/400) boxes. That's important because more than 19,000 mainframes and several hundred thousand iSeries machines are in regular use worldwide. Here's what you need to know about HIS 2004.

Network Connectivity
You can use HIS 2004's new Visual Studio (VS) integration piece to take logic from a mainframe and expose it as Web services from a Windows Server machine. That means you can now take legacy CICS and Information Management System (IMS) mainframe applications and iSeries–based applications, publish them as Web services, and open them up to a much wider range of standards-based applications and services without having to touch the mainframe or change the legacy applications. The design environment that enables this functionality is hosted in Visual Studio .NET 2003 and is almost completely graphical.

To make this functionality possible, Microsoft upgraded the COM-based transaction coordinator from earlier HIS releases to the new .NET–based Transaction Integrator (TI). In addition to supplying XML Web services capabilities to legacy applications, this technology also includes import and export code wizards for COBOL and RPG.

Additionally, a new Microsoft Message Queue Services (MSMQ)-MQSeries Bridge lets administrators more easily link transactional applications running on different platforms, creating an interplatform message-queuing capability. This feature supports MSMQ 2.0 and MQSeries 5.1.

Finally, HIS 2004 offers a service that lets SNA-based applications running on IBM mainframes interoperate with HIS 2004 over IP-based networks. This service will let enterprises replace legacy networking hardware with standard Gigabit Ethernet networking hardware, saving money and improving performance.

Host-Initiated Processing and Application Integration
In HIS 2004, Microsoft has added functionality called Host-Initiated Processing (HIP), which is essentially the opposite of Windows-Initiated Processing (WIP) and answers many of WIP's limitations. With HIS, a mainframe application can act as a client and call another application residing on a mainframe, an iSeries box, or a Windows Server machine. On the Windows end, Microsoft supplies listener services to make this functionality work. These services use the same message formats that mainframes use and behave identically to mainframe applications. Thus, a Windows box can act as a peer to a mainframe.

The application-integration functionality uses Windows single sign-on (SSO) technology to pass user credentials between the machines. On the Windows side, the services challenge Active Directory (AD) to see whether the user account under which the application is running has the proper credentials to continue. If it does, the application runs and returns the results to the originating application on the mainframe.

Furthermore, the HIS development environment now runs from within Visual Studio .NET 2003. Programmers can use standard Visual Basic .NET code, for example, to write applications that exchange data with mainframes. HIS also has a Microsoft Management Console (MMC)–based administration tool for deploying these applications, letting you take advantage of the native capabilities of Windows Server-based machines, including load balancing and clustering.

Data Interoperability
HIS 2004 ships with standard ODBC, OLE DB, and .NET drivers for DB2, allowing programmers to access DB2 databases in the same manner they access other Windows-based databases. Microsoft has enhanced the DB2 network protocol client to support two-phase commit (2PC) for IP-based distributed transactions.

Recommendations
HIS 2004 is available in standard and enterprise editions. HIS 2004 Standard Edition includes all networking, security, SSO, and data-integration capabilities; HIS 2004 Enterprise Edition adds application integration functionality, such as HIP, Windows-Initiated Processing, and MSMQ-MQSeries bridging. If you're looking to access mainframe- or iSeries-based applications or data from Windows Server machines, HIS 2004 is likely your best choice. With HIS 2004, Microsoft isn't trying to move you off your existing platform but has recognized that many customers will want to interoperate with those platforms for years to come.