IBM Unveils New z/OS, Says Goodbye to OS/390

IBM Corp. announces release 1.4 (R4) of z/OS.

• By Stephen Swoyer
• 08/22/2002

First, the bad news: In tandem with its release of R4, Big Blue has disclosed plans to discontinue new sales of OS/390 as of Dec. 17, 2002. IBM also plans to discontinue break-fix support for OS/390 by Sept. 30, 2004.

According to John Phelps, vice president and research director of servers and storage with consultancy Gartner Inc., a move of this kind could affect a substantial number of customers—including many who now run OS/390 on zSeries mainframes.

"About 40 percent of the z900s that are installed are running z/OS today, the rest are running OS/390," Phelps comments.

That’s because the z/OS licensing agreements explicitly prevent users from operating z/OS in 31-bit mode, says Mark Zelden, a systems programmer and consultant with Zurich American Insurance Co. Although Zurich American is currently in the midst of a migration from 31-bit OS/390 release 2.10 to z/OS R1.3, Zelden says that he understands why most mainframe shops —including several of his former consulting clients—have been slow to embrace z/OS on the newer zSeries hardware.

"When IBM introduced z/OS, if you wanted to run z/OS on a zSeries machine, you had to be running in 64-bit mode, according to the terms of the license you had to sign," Zelden explains. "Also, if you tried putting it in 31-bit mode, the system wouldn’t IPL correctly, [because] some of the original programmers never programmed for that possibility."

Now, for the good news. According to several industry watchers, there’s far more good than bad in IBM’s z/OS-related announcements. It begins, not surprisingly, with the issue of 31-bit support on z/OS.

"IBM is going to be able to offer a special six month fall-back capability for people, such that if they move to z/OS 1.4, they can fall back for six months into 31-bit mode, so they can actually run in 31-bit mode on z/OS," confirms Gartner’s Phelps.

The fall-back, which IBM has officially branded the z/OS Bimodal Migration Accommodation, is intended to give new and existing customers time to test 31-bit applications on z/OS. IBM indicates that the fall-back period will commence as soon as a customer licenses z/OS on a server. As a result, says Gartner’s Phelps, it should appeal to the 60 percent of customers who run OS/390 R2.10 on zSeries mainframes.

New Update Schedule
Also noteworthy, says Charles King, a senior industry analyst with Sageza, formerly Zona Research, is IBM’s decision to adopt an annual, rather than a bi-annual, release schedule for new versions of z/OS. "Updating a new mainframe OS is not a trivial matter, and I think that if there’s a message here, it’s that IBM in essence is saying to their mainframe customers that when we roll out a new iteration of the z/OS, you’ll have 12 to 14 months to enjoy the benefits of that before we bring out the next version."

Mainframe shops are often portrayed as static environments in which very little ever changes. According to programmers such as Zurich America’s Zelden, however, big iron shops often experience pressure to migrate to new versions of IBM’s mainframe operating environments in order to maintain coexistence support for legacy platforms and applications. Prior to z/OS R4, for example, IBM typically supported coexistence on an n-3 basis, such that it would guarantee the coexistence of its current operating environment, along with the three operating environments that preceded it. Since Big Blue typically shipped a new version of its mainframe operating environment once every six months, customers typically were faced with upgrade scenarios every 18 months.

Starting with z/OS R4, IBM will still support coexistence on an n-3 basis, says Gartner’s Phelps, but customers will enjoy the same duration of coexistence support—three years—as they do break-fix support.

According to Evelyn Trotter, senior software engineer with IBM's z/OS product development team, when the annual release cycle begins in September, 2004, "New z/OS and z/OS.e functions will be delivered between releases through the normal maintenance stream or as Web deliverables. In addition, significant new function may be delivered between releases as features of the z/OS product."

IBM’s shift to an annual release schedule has been warmly received by value-added resellers (VARs) and solution providers, as well. Tony Madden, vice president of sales for the IBM business unit of Avnet Hall-Mark, a major IBM VAR and solution provider, says that the move is a good one for end users and resellers alike.

"It means that they can better package and deliver more functionality at once than [they could] on an aggressive time table. But they’re doing it on a better schedule," he observes. "It’s a good move, because for our customers, their biggest challenge is managing the change. This helps them to do that."

The new z/OS R4 release has important implications for customers with G5 or G6 mainframes in-house, adds Gartner’s Phelps. "If you take a look at all of the G5 and G6 boxes that can run z/OS, most of them are holding on OS/390 [release] 2.10. [These customers are] getting to the point where they’re going to have to do something."

As a result, IBM indicates that z/OS release 5 (R5)—which is slated to ship not in September 2003 but in early 2004, will support G5 and G6 systems. The upshot of this, Phelps notes, is that G5 or G6 shops that upgrade to R5 will enjoy platform coexistence and break-fix support from IBM through 2007.

"Obviously they’re not going to get anything new [after R5], but they will be supported. That’s very important to these customers," he points out.

Regardless of whether they’re running OS/390 on G5, G6 or zSeries hardware, Phelps says that z/OS R4 will mark the last release in which customers will be able to move from the final version of OS/390—2.10—to z/OS in one step. Adds Evelyn Trotter, "z/OS 1.4 will be the minimum level required for the console availability feature. OS/3902.10 customers are strongly encouraged to move to z/OS 1.4."

Despite the news that IBM has disclosed plans to discontinue sales of OS/390, users such as Zelden perceive the new z/OS release as a mostly positive development for mainframe customers. "I’m very pleased with the announcement. I see it as overall a very good thing, in particular the extended [coexistence] support and the ability to run in 31-bit mode on z/OS," he concludes.