Thin-Client vs. Fat-Client in the Host Connectivity World

With the widespread introduction of Web-enabled thin-client terminal emulation software products over the past several years, the world of host-access technology has seen a dramatic change. Thin-client host connectivity technologies have extended the accessibility of mainframe and midrange systems in this Web-focused era, and a 1998 Datapro study reported that many information systems professionals have arrived at the conclusion that thin-client Web-to-host technologies spell the certain and imminent demise of fat-client PC-to-host connectivity technologies. Similar predictions as to the death of the mainframe system have proved inaccurate. In fact, mainframes today remain the cornerstone of legacy systems and are as relied-upon as ever before. According to industry estimates, approximately 70 percent of business data still resides on mainframe hosts and about 75 percent of mission-critical mainframe applications are terminal-based. Industry analyst Gartner Group estimates that production workers account for 85 percent of host application users, with most using terminals or PC-based terminal emulation software for host access.

What has changed is the pathway to host data and applications; there are now two basic means of host connectivity, and the challenge is to find the best solution for functionality that matches end-users’ needs. Thin-client solutions provide an additional option for 3270/5250 terminal emulation, along with integrated access to data residing on diverse legacy system hosts. As Gartner Group reported earlier this year, comparative differences in functionality make Web-based terminal emulation technologies suitable for different classes of users than traditional PC-to-host connectivity products.

Despite the forecasted appearance of a generation new thin-client terminals, vast numbers of "dumb" terminals remain in organizations around the world. A 1997 Dataquest Perspective estimated approximately 30 million seats available for the terminal market, with a 4 percent annual growth rate, creating a significant market opportunity for many Web-to-host software vendors. Wholesale replacement of dumb terminals with thin-client web-to-host software, however, may be limited to sharply focused market segments and defined user groups within organizations. Users who have come to rely upon high performance may continue to need PC-to-host software, and Web-to-host solutions may be most attractive to organizations requiring secure and cost-controlled Intranet and Extranet access.

Before continuing this discussion, here are some definitions for the record. Fat-client PC-to-host connectivity refers to access to host data from a single personal computer or network of PCs to information on host systems through a locally installed software application. Thin-client Web-to-host connectivity provides access to information on host systems through a server-based connectivity software application.

Faced with demands for Web-based connectivity from upper management, business partners, and some end-users, many enterprise systems administrators and vendors may find themselves challenged to evaluate available technologies and decide whether or not to recommend a shift to thin-client technology for host access. Thin-client benefits and advantages-including cost-efficiency, simplified administration, and reduced training time-are accompanied by weaknesses and limitations as an enterprise-wide solution for all of the many specific types of access to business-critical data and applications that users require. In a recent report on web-based terminal emulation in the healthcare enterprise environment, Gartner Group concluded that such product decisions must be based on suitability of the software for the specific type of user, with consideration given to the level of desktop control needed.

The perception that thin-client Web-to-host technologies will soon replace fat-client PC-to-host software tools seems to be in contrast with the reality of the host connectivity world as seen by connectivity software manufacturers positioning thin-client and fat-client host-access tools as complementary rather than exclusive technologies-offering enterprise computing professionals unique solutions for unique groups of end users.

As the Connectivity World Turns

In the recent past, fat-client technologies were the only real game in town for terminal emulation and host access. Vendors offered fat-client PC-to-host products across the board to anyone and everyone who needed connectivity for access to IBM mainframe, AS/400, Data General, Digital, and Unix hosts-or any various combinations of these and other host types. In today’s information-dependent world of mergers, acquisitions, and consolidations, access to legacy systems is critical to the success of organizations of all types and sizes. As organizations add new hosts, manage the migration to new platforms, and develop Intranets and Extranets, enterprise systems administrators look for solutions that keep up with their organizations’ technological growth and changing connectivity requirements. Thin-client web-to-host access provides new alternatives for host connectivity, although not necessarily at the exclusion of existing fat-client PC-to-host solutions.

Since thin-client computing emerged just a few years ago in 1996, Web-based technology has proliferated and enterprise systems Administrators’ interest in central network management has continued to evolve. Interest in networking technology in general has increased as the advantages of centralized computing environments have become increasingly apparent to organizations of all sizes, and thin-client products have gained much attention as a low-cost host connectivity solution. Whereas in the recent past thin clients were seen as technological upgrades for terminal emulation applications, Web-to-host connectivity software products are now beginning to be recognized as an additional tool offering specific types of functionality to meet user needs.

Considering the diversity of today’s enterprises, common sense would suggest that the thin-client versus fat-client issue is not an all-or-nothing case of "out with the old, in with the new." Rather, it appears to be a matter of expanded options and additional capabilities for end users and those who are responsible for providing and administering host access. With the availability of thin-client technologies in addition to fat-client technologies, enterprise systems administrators can take advantage of increased opportunities for greater flexibility in selecting the best solutions for their specific host connectivity challenges. The chart below shows some of the features that typically differentiate thin-client Web-to-host and fat-client PC-to-host connectivity software products.

Feature Fat-Client PC-to-Host Thin-Client Web-to Host

User control over Yes No

Desktop customization

SAA or Serial support Yes No

Remote-access capability Limited No

Security No Yes

Centralized management No Yes

and administration

"Screen-scraping" No Yes

Multiple-platform support No Yes

Table 1


One Size Doesn’t Fit All

Using the maxim "the best tool for the job" as the overriding factor in evaluating host-access solutions, specific network architecture conditions and information-access requirements that create the need for a thin-client Web-to-host solution can differ vastly from those that create the need for a PC-to-host product. Assessing host connectivity needs in today’s corporate and government information environments requires a thorough understanding of the distinctions that exist between specific host-access challenges and the respective solutions that PC-to-host and Web-to-host technologies offer. Although a thin-client product may be an easy-to-use and cost-effective connectivity solution for certain types of uses, such as basic access to applications and retrieval of data, that same tool may be inadequate and inefficient for "power users" whose information-access needs and productivity objectives demand a much higher level of software performance and host interactivity.

Of course, thin-client and fat-client technologies do not, by themselves, determine the particular kinds of connectivity that diverse users and organizations need-users’ data-access requirements define an enterprise’s need for host connectivity. Therefore, implementing a user-focused approach to connectivity design would seem to be the most direct way to arrive at a seamlessly functional solution for accessing host and legacy systems by way of a thin-client solution or a fat-client solution, or both-depending upon what best satisfies the users’ specific host-access requirements in consideration of all other network factors.

Further, it seems likely that organizations across a broad range of business sectors and network architectures might benefit from an integrated combination of fat-client PC-to-host and thin-client Web-to-host technologies as an optimum solution for host connectivity throughout the enterprise.

Thin-client and fat-client technologies both offer the capability to help administrators ease migration to new platforms, integrate diverse hosts and applications, support multiple protocols, extend legacy system capabilities, deliver accurate emulation, automate common tasks for increased user efficiency, and reduce training time and overall computing costs. In the final analysis, the specific needs of particular organizations’ users determine whether the best choice is a PC-to-host fat client, a Web-to-host thin client, or both.

Some end users may actually view a sudden enterprise-wide shift to thin clients as a threat to their freedom and ability to do their jobs well. Forcing everyone to adapt to a thin client might even result in a backlash of complaints from users who face high-productivity expectations and rely upon specific types of capabilities to meet those expectations. If asked which they prefer, most of those users will probably say that they want the flexible fat-client capabilities to which they have become accustomed. After all, technology equates with power; end users may not want to give up control.

Even organizations that currently use thin-client host connectivity or plan Web-to-host deployment in the future may recognize that some end-users simply require fat-client capabilities in order to perform their particular job functions most efficiently. To those employees, a thin-client mandate might even give the impression of oppressive top-down management philosophy that is out of touch with employees’ needs. Taking away computing control can send a negative message. Of course, other end users who don’t need that control - the inexperienced or occasional variety who only require relatively simple access to the mainframe or midrange - may welcome with open arms the thin client’s simplicity and ease of use.

Weighing the Options

Fat-client PC-to-host solutions deliver the high-performance connectivity and host-interaction flexibility that many end users demand. Experienced and frequent users often derive valuable benefits from having the direct access to powerful customization, automation, and integration tools of a full-featured fat client. The rich functionality of fat-client PC-to-host solutions may even help to increase user productivity by providing user-customized ways to get the particular job done most efficiently.

For Atlas Specialty Steel of Canada, replacing terminals required exact and problem-free PC-to-host connectivity for reliable access to business-critical applications. "We needed a quality terminal emulator that would run on a desktop PC and allow our users to interact with the host environment," said Brian Fear, Technical Support Specialist for Atlas. Describing Atlas’ PC-to-host connectivity solution, Fear said "It simply is a superior terminal emulation package."

Thin-client Web-to-host solutions can provide the attractive benefits of single-point installation and centralized administration for efficient host access. They are especially useful for intranet and extranet access, and some products include strong security capabilities to safeguard access by remote users. Because installation, configuration and upgrading take place at the server, thin-client solutions can help to control maintenance costs and potentially even help reduce total cost of ownership. Additionally, the intuitive browser-based interfaces provided by some thin-client software products offer ease-of-use benefits for the occasional users who make up 10 percent of those who access host applications, according to Gartner Group.

The Best of Both Worlds

To appreciate the value of employing both types of host-access technologies as complementary solutions, consider the high number of organizations around the world that are continuing efforts to replace terminals. Gartner Group estimates that pockets of installed fixed-function terminals remain in approximately 80 percent of large enterprises today. As those organizations assess the need for replacement of their terminals and investigate various solutions, two basic levels of requirements may become apparent: one that is best met by the customization capabilities and high performance of a fat-client solution, and the other by thin-client efficiency and remote-access security.

For example, a healthcare organization with fat-client users who individually automate and customize mainframe data for specific purposes may also want to give physicians anytime/anywhere access to patient records and lab test results with a thin-client Web-to-host solution.

Such is the case with Fairfax Family Practice Centers (FFPC), a 10-site family physician group practice in the northern Virginia suburbs. "We needed a simple method so that anyone from anywhere can gain access to our Practice Management System," said Scott Lemler, Director of Information Services for FFPC. "Physicians who are on call will now be able to gain access to all our patients’ medical information any time - day or night - from their offices or from their homes. In evaluating PC-based terminal emulation packages, we felt that it was important to select a product that was simple to use, install, and manage. A Web-server based product was our best bet."

Or, a financial institution may have home-office representatives who need account-specific access to host information, while the company’s field representatives may require much more limited access but with far greater security to protect sensitive and personal customer data. The good news is that these choices are, and will continue to be, readily available - often from a single vendor who can provide compatible products with similar features and capabilities backed by technical support from a common source.

Rather than a new technology that will sweep through the enterprise and make fat-client PC-to-host solutions obsolete, thin-client host connectivity seems to reflects a computing style that is relative to specific types of users. Large enterprises in particular may benefit from deploying thin-client Web-to-host products to a percentage of users in addition to those who use a fat-client, including employees who may not have had host access in the past. Enterprise systems administrators and vendors will want to assess end user needs throughout the enterprise, then examine deployments of host-access solutions according to those user types.

The centralized management and advantages of a thin-client Web-to-host solution address cost-containment and decreased support needs while extending secure host access to remote users. For users requiring flexibility and control of multiple functions at the desktop, a fat-client PC-to-host tool may be a better solution. What administrators and vendors will not want to overlook in any evaluation of host connectivity needs, however, is the fact that both types of users may be present in the enterprise for years to come.


Lynn Weatherby is Director of Product Planning and Management for Persoft, Inc. (Madison, Wis.; She can be reached at (608) 273-6000.

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