Linux on the IBM S/390

Linux/390 in the Spotlight at SHARE 94

by Jack J. Woehr

The atmosphere at SHARE 94 in Anaheim, California was nerdy beyond the ability of mere Unix hackers to imagine. Big draws at the conference, held March 5-10, 2000 at the Anaheim Hilton and Mariott, included sessions examining the latest updates to S/390 assembler programs and exhibits of computers the size of walk-in closets. Attendees included over three thousand members and scores of vendors displaying millions of dollars of hardware and software. Evening wining and dining was grouped by tables manned by interest groups tracking particular applications such as MQSeries and REXX. White beards and suspenders abounded, identifying senior engineers, many of whom possess over thirty years of industry experience. One attendee, pondering the future of mainframing, opined that "our average age is over 50 years old," and wondered aloud about who is going to maintain these still-vital and mission-critical legacy systems when the current work force retires.

But the most popular attractions this year, inevitably filling meeting rooms to overflowing, were the sessions about Linux on the S/390. The air was electric with excitement about this revolution from below, which has drawn the world's largest intellectual property holding company, IBM, into communion with the open source community.

IBM representatives are pleased but obviously somewhat stunned by the attention garnered both inside and outside their customer base by a small collection of source diffs posted to an off-the-beaten-track web page. One cautious view among the managerial cadre is that Linux/390 may be a means to stem the decades-long erosion of interest in mainframe computing and draw mindshare back to this mature and stable field. Another faction has it that this debate had been settled inside IBM in the early 1990s when OS/390 Unix System Services became the officially designated solution path, and that support for Linux overturns stare decisus, undermining that which was assumed to be a "done deal" in the internal politics of the multinational IBM corporate city-state.

One indicator of the internal schism is that while IBM is trumpeting their open source Linux/390 work, one of the participants in the project is being menaced with disciplinary action for his unsanctioned but seminal role in the project, despite the fact that he did the work on his own time. There is every possibility that Linux/390 would never have been shown outside IBM had that organization not been goaded by the alternate certainty of an entirely non-IBM Linux port.

Although the OS/390 (formerly known as MVS) operating system, which serves the terabyte database needs of organizations such as the IRS and Bank of America, is the flagship of S/390 offerings, the minority VM/ESA community is home of the real metalheads in this crowd. They sometimes refer to VM as the "original personal computer."

VM evolved to suit the needs of the "real programmers," many of whom are as passionate about VM as today's young whippersnappers are about Java. While these enthusiasts know that for technical reasons VM will never depart the glass house, many worry that VM is generally receding from the landscape as a user operating system. They believe that the ability of individual users to run shared instances, personal instances, and application-specific instances of Linux/390 under VM will breathe new life into the old workhorse. We spoke with a select group of crossover VM-Linux/390 folks about this novel development.

DDJ thanks Marty Zimelis of Sterling Software for assistance in arranging our conversation. Thanks are also due to many other SHARE attendees who took time to chat with us about S/390, VM and Linux. Among these were Alan Ackerman, John Franciscovitch, Bill Bitner, Erich Amrehn and Melinda Varian. We also spoke with Linas Vepstas.