IBM's mainframe and midrange operating systems hold a slowly diminishing lead over Unix and Windows NT in high-end computing, analysts said.
But analysts also consider Windows NT - not Unix - as the main threat to these IBM platforms, even though research shows that Unix holds a solid enterprise computing lead over Windows NT.
Analysts say this is because the mainframe OS/390 natively supports Unix application programming interfaces and, therefore, Unix applications.
At the same time, the AS/400 midrange system already supports 64-bit computing, something many variations of Unix are still trying to perfect. OS/400 won't support Windows NT natively, but the AS/400 carries an Intel-based PC board that soon will be able to run Windows NT applications in the AS/400 box.
Gartner Group says IBM will continue to invest in research and development on the OS/390 through 2001, but the research firm also says IBM will slowly shift its focus to support existing S/390 customers.
And as Unix and Windows NT servers ramp up their performance to mainframe levels, Gartner expects IBM to shift to Windows NT as its most strategic, general-purpose enterprise platform by 2001. For example, OS/390 will support Windows NT application interfaces this quarter.
The OS/390 has received strong support lately from software giants that port their applications to the platform, and IBM has launched the OS/390 Partners in Development program to maintain user interest in OS/390.
IBM's release of a version of OS/390 on the RS/6000 Unix platform also has given third-party developers a low-cost way to test and convert their applications. That version has been dubbed the R/390.
"Before [the R/390], testing [on the S/390] would have been a bet-your-company investment" because companies had to buy a high-end mainframe for application development, says Tom Laffey, vice president of engineering at Talarian Corp. in California.
The firm is releasing an S/390 version of its middleware, which previously ran only on Unix.
With the S/390's low-end offerings and packages, users have more flexibility than ever to get OS/390 reliability and power in whatever price range they want, says Mike Kahn, chairman of The Clipper Group Inc., a consultancy in Wellesley, Massachusetts.
Ed Carr, an analyst at Aberdeen Group Inc. in Boston, says the OS/390 will bring its mainframe capabilities downstream enough to battle Windows NT on its own turf.