To split or not to split? Tools little help answering - includes related article on Cooperative Solutions Inc - Client/Server Computing: Development Tool Status Report - tutorial

Software Magazine, Feb, 1991 by Paul Korzeniowski

ON0075

You have listened to the talk about microcomputer technical advances, and have seen advertisements for microcomputers claiming to possess mainframe power. You have read about firms saving millions of dollars by replacing terminal-to-host applications with client/server applications, some running on microcomputer local-area networks (LANs) and others connecting microcomputers to mainframes. You have wondered if your finn could reap similar benefits. Can it?

In some cases, yes. In others, no. That answer probably falls short of what a manager would like to hear, but unfortunately, there are few guidelines and fewer software tools that help users determine if client/ server applications can save their firms money. "When examining a client/server application, users quickly realize that current technology is far ahead of system and performance management tools," noted Phil Hartley, programming technologist at American Airlines, Inc., Dallas.

For companies like American Airlines, help is coming-slowly. Industry pundits do not expect comprehensive tools to be commercially available for three to five years. The lack of tools probably will slow many firms' transition to client/server applications, but eventual implementation of such applications appears inevitable.

During the past few years, many firms have replaced mainframe applications with LAN applications, or have connected microcomputers to mainframes. For instance, Tex/Con Oil & Gas Co., Houston, is replacing payroll and human resource applications that currently run on an IBM 3084 mainframe with LAN applications. The existing applications, which have been used for years, support more than 200 users.

From such examples, certain pundits have proclaimed that mainframes are quickly becoming extinct. In reality, the mainframe is still the only platform capable of supporting many business functions. What has become unclear is the dividing line that determines when an application should be run on a mainframe and when a smaller computer is appropriate.

Application size is the most obvious dividing line. "Some of our large applications work with more than 1 terabyte of online storage and pull information stored in 25 CICS regions on half a dozen different mainframes," explained Brad Moore, a programmer analyst at DST Systems Inc., a financial services firm in Kansas City, Mo.

"Obviously, a LAN is not powerful enough to support applications that large," he added. While a mainframe can work with 1 terabyte of central storage, a microcomputer's high-water mark is usually only 32M bytes.

The number of users can also serve as a good dividing point. Generally, mainframe applications that support hundreds of users, can be moved to LANs. When the number of users reaches the thousands, then a mainframe usually is required.

Disk storage is another area where mainframes have a huge lead over LANS. The maximum capacity on a NetWare LAN from Novell Inc., Orem, Utah, is 32T bytes compared to 500T bytes on an IBM 3090.

"Many LAN peripherals simply do not work fast enough to support applications that require a lot of disk storage," said Malcolm Colton, technical programming consultant at Sybase Inc., Emeryville, Calif. "In some cases, backing up data can literally take hours."

Other LAN limitations stem from how data is used. In certain cases, LANs have sufficient storage and processing power to complete most transactions, but exceptions can grind networks to a halt. Richard Finkelstein, president of Performance Computing, Inc., a Chicago consulting firm, noted, A LAN server would take hours to sort one million records."

Report generation also can stretch LAN limitations. "If a user simply accesses a few rows of database information, then a microcomputer LAN can certainly support the application," said Colton. "If users are constantly generating complicated reports, then an application may require a more powerful server."

APPLICATION REWRITES DAUNTING

Another reason to keep mainframe applications is the difficulty in rewriting them for LANs. "In many companies, mainframe programs evolved during 20 years, and the original programmers left the company long ago," said Colton. "How applications function is a bit of a mystery, so corporations are leery of making any changes because they could bring mission-critical systems down."

Often, rewriting is a task too great for many firms. Tex/Con Oil and Gas has been offloading applications from a time-shared mainframe to LANs running the Vines operating system from Banyan Systems Inc., Westborough, Mass. However, the firm stopped short of downsizing a set of gas marketing applications.

"We purchase only turnkey software programs, and have not been able to find a good LAN gas marketing application," said Bill Shearer, the director of computer services. We do not want our programmers spending their time writing new applications."

Usually, companies rewrite existing applications only when they become obsolete. Corporations will not rewrite applications simply to take advantage of current technology," reported Finkelstein at Performance Computing.