• Sidebar: HIS Capabilities
• Illustration: Levels of Host Integration

A new version of Host Integration Server (HIS), Microsoft's middleware product for linking Windows applications to mainframes and AS/400 systems, helps developers expose some types of host applications as Web services, and can also make Windows applications appear as mainframe applications, allowing organizations to offload some processing onto Windows-based servers. However, many of the most compelling new features are available only on a new, more costly Enterprise Edition.

Legacy Applications Live On

A strong argument can be made that Windows servers can offer business applications mainframe-class levels of reliability, availability, scalability, performance, and access to massive databases, at lower cost and with faster development time. Nonetheless, the fact remains that very few mainframes are being retired. Even applications written more than a decade ago for IBM’s mid-range AS/400 systems live on, with replacement by modern Intel-based servers happening infrequently. In fact, IBM has a healthy business selling newer models of System 390 mainframes (now called zSeries) and the AS/400 (now called iSeries).

Even though many industry pundits and wishful PC hardware and software vendors have predicted the imminent demise of these systems, and development of new applications for these legacy systems is rare, most remain in place, primarily for the following two reasons:

Benefits do not outweigh costs or risks. The cost of converting organizations’ legacy software assets—business data and highly customized custom application code—to run on cheaper platforms (such as Windows, Unix, or Linux) is significantly greater than the cost of maintaining those applications on legacy hardware, even though most legacy applications are awkward to manage and difficult to modify. Consequently, there is rarely a reasonable expected payback for any such project, especially when factoring in risks such as business disruption or failure of the project. In addition, new functionality that could be added to the application during such a migration can rarely generate enough incremental business benefits to tip the balance in favor of migrating.

Integration products extend the life of legacy software. The availability of middleware products, such as HIS, that allow organizations to extend the life their legacy software and gain many of the benefits of more modern systems, such as graphical user interfaces, rapid application development, and componentized architectures, further reduces the motivation to migrate.

Microsoft expects legacy applications to remain in widespread use for the foreseeable future, and it plans to continually enhance HIS and other Microsoft middleware products, such as BizTalk Server, to further improve integration between Windows and host applications and data. Microsoft’s goal for HIS is to make sure that the Windows platform and Visual Studio development tools provide the best means for developers to extend the life of legacy applications and data, especially when compared with alternatives based on the Java 2 Enterprise Edition platform from vendors such as IBM and BEA.

What’s New in HIS 2004?

The new release does not fundamentally change the scope of HIS. Like its predecessor, HIS 2004 is a "Swiss Army knife" product with different features targeting various integration scenarios. Using HIS, a Windows system can connect into a host application at three distinct points:

User interface. The Windows system can send input to the legacy application and present its output using the original interactive user interface (for character-based terminals) or batch input/output interface of the host application.

Business logic. The Windows system can make calls to legacy applications that have programmatic interfaces to their business logic code, either through a host transaction processing system, namely, IBM’s Customer Information Control System (CICS) or Information Management System (IMS), or through a message queuing interface, namely, IBM’s MQSeries (recently renamed WebSphere MQ).

Data. The Windows system can access data from DB2 databases or data files used by host applications, using the native IBM host protocols for connecting to those data sources.

All three approaches require network integration to connect the Windows system to the host, and security integration to enable sign-in and secure data exchange with the host.

(Readers unfamiliar with mainframe integration and HIS capabilities should read the sidebar "HIS Capabilities", and see the illustration "Levels of Host Integration".)

Business Logic Integration Improvements

HIS 2004 includes a component for business logic integration called Transaction Integrator (TI), formerly called COM-TI. COM-TI allows developers to expose host applications as distributed COM (DCOM) objects callable by other Windows applications, enabling the Windows applications to initiate transactions with the host—a process known as Windows Initiated Processing (WIP).

The new TI extends WIP to support the .NET Framework object system and Visual Studio .NET 2003. This enables developers to expose some types of mainframe and AS/400 applications as Web services, which are callable from other .NET applications, BizTalk Server, and applications on other platforms that support Web services protocols. This new capability makes it easier for developers to build modern service-oriented architectures that incorporate their legacy systems. (See "Principles of Service-Oriented Architectures" on page 23 of the June 2004 Update.)

Also, TI supports new programming models in support of enhancements IBM made to its CICS and IMS mainframe transaction processing systems, such as persistent CICS connections.

New in HIS 2004, TI supports Host-Initiated Processing (HIP), an integration approach that allows a Windows server application to function as a "peer" to IBM mainframe and AS/400 applications. HIP can be advantageous when an organization needs to rewrite one component of a more complex mainframe application: developers can rebuild the component using Windows development tools and host it on Windows products, such as Windows Server, BizTalk, or SQL Server. HIS emulates the API of the old mainframe component and performs all the needed translations required by the Windows application such that, to the calling mainframe components, nothing appears to have changed.

TI includes TI Designer, which plugs into Visual Studio .NET 2003 and is used for building the host application wrappers (i.e., "proxies") used in both the WIP and HIP integration approaches. TI Designer can import mainframe or AS/400 COBOL-based or RPG-based data definition source code, and it then provides tools that help the developer map these data definitions to .NET classes. TI Designer tools also integrate with HIS’s single sign-on capabilities so that security credentials map properly between the host and Windows environments.

Like its predecessor, HIS 2004 includes a messaging bridge feature that translates between MQSeries messages and Microsoft Message Queuing (MSMQ), thereby enabling integration of mainframe and AS/400 applications that expose MQSeries message queue interfaces.

Data Integration Improvements

HIS 2004 includes a new ADO.NET data provider that allows .NET applications to read and update records in IBM’s DB2 database. As with its predecessor, HIS 2004 also includes the DB2 ODBC driver, DB2 OLE-DB provider, and OLE-DB Provider for AS/400 and VSAM files.

Because mainframe, AS/400, and open server editions of DB2 use IBM’s Distributed Relational Database Architecture (DRDA) protocol for making database calls over a System Network Architecture (SNA) or TCP/IP network, HIS must be installed on each Windows server making the DB2 database calls. The HIS network client for DB2 handles all of the DRDA protocol conversions on behalf of the data providers (managed, OLE DB, and ODBC).

Previously, when developers wanted to write records into the DB2 database, HIS 2000 provided support for reliable two-phase commit (2PC) distributed transactions, but only over an SNA network. HIS 2004 extends 2PC support to IP-based networks, and the DB2 data providers have been enhanced to include advanced capabilities, such as returning multiple results on calls to DB2 stored procedures, as well as password expiration and database change management. In HIS 2004, SQL Server Data Transformation Services can read/write directly to mainframe or AS/400 file systems using the OLE DB Provider for AS/400 and VSAM.

Networking Improvements

While HIS 2004’s base network functionality remains largely unchanged, it gains two important new enhancements:

IP-DLC link service. For some time, IBM has supported direct mainframe connectivity over TCP/IP by using a protocol called data-link switching (DLSw). This protocol provides a way to tunnel SNA traffic over an IP network, eliminating the need for expensive SNA leased lines or data-link control bridges to connect SNA hosts to terminals and printers. However, standard IP routers are not compatible with DLSw, forcing organizations using DLSw to purchase expensive specialized routers.

A newer protocol, called High Performance Routing over IP Data Link Control (HPR/IP-DLC), also tunnels SNA traffic over IP but, unlike DLSw, does not require special routers and, more importantly, eliminates the need for expensive IBM 3746 front-end processors (FEPs) attached to the mainframe. Organizations can use HPR/IP-DLC to link Windows applications at one location to a mainframe in another over a normal IP-based WAN: the Windows applications connect to a local HIS server, which in turn uses its HPR/IP-DLC link service to communicate across a WAN with the mainframe. This is an especially important feature because many customers are retiring FEPs over the next year, in response to the end of support life cycle for the IBM 3746.

TN3270 session encryption. TN3270 emulates an IBM 3270 terminal on a PC using an adaptation of the TCP/IP Telnet terminal emulation protocol (normally used for establishing terminal sessions with Unix systems). TN3270 users can connect directly to an IP-enabled mainframe or an IP-SNA gateway without requiring SNA components on the PCs. Although HIS 2000’s TN3270 service offloads the mainframe from having to perform the nonnative TCP/IP-to-SNA conversion required to support TN3270 clients, the TN3270 keystroke and screen data passing over the network is unencrypted, which could expose security credentials or sensitive information to network eavesdroppers.

HIS 2004 includes support for using Secure Sockets Layer Transport Layer Service (SSL-TLS), allowing customers to use a certificate and public key encryption to secure TN3270 traffic between users’ PCs and the HIS server.

Two Versions, More Expensive

In keeping with its strategy on many Windows Server System products, Microsoft decided to split HIS 2004 into Standard and Enterprise Editions. The Standard Edition of HIS 2004 includes all of the lower-level network and security features, plus the data-access drivers and providers. The Enterprise Edition adds both the Transaction Integrator and the MSMQ-MQSeries Bridge features for integrating host applications.

Unfortunately, customers who only need HIS 2004 Standard Edition do not save any money as a result of this repackaging; pricing is unchanged from HIS 2000’s US$2,500 per processor. Furthermore, customers who need the Transaction Integrator or the MSMQ-MQSeries Bridge will need to purchase the much more costly Enterprise Edition for US$10,000 per processor.

Existing HIS 2000 and SNA Server 4.0 customers can upgrade their servers in place to HIS 2004. Customers who purchased HIS 2000 with Software Assurance are entitled to upgrade to either HIS 2004 Standard or Enterprise Edition as part of their SA benefits. When their Volume Licensing agreement expires, customers are entitled to renew their Software Assurance only for the HIS 2004 edition they select for their upgrade.

Both HIS 2004 editions require either Windows 2000 Server or Windows Server 2003. Developers can also install it on Windows 2000 Professional Service Pack (SP) 4 or Windows XP Professional SP1 for development purposes.

No Microsoft Operations Manager (MOM) 2005 management pack has been issued for either version, although the MOM 2000 management pack for HIS 2000 will continue to work with HIS 2004. At the May 2004 TechEd, Microsoft committed to issuing MOM management packs for all of its 2005-series server products, and even though the HIS 2004 product predates that series, the HIS product group is currently working on a new MOM 2005 management pack, although no availability date was given.

Resources

More information and a trial version of HIS 2004 can be obtained at www.microsoft.com/hiserver.