Operating Systems

The VSE Operating System State of the Union

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IBM has made several announcements in recent years that affect which versions of the VSE operating system are still available to customers and which versions are still supported for service. This article reviews these announcements and their implications for the hardware platforms on which customers are still running VSE.

VSE History: A Hardware and Operating System Evolution

What we know today as the VSE operating system began more than 40 years ago. Throughout its history, VSE customers have had to make both hardware and operating system upgrades to take advantage of new technologies. What follows is a brief review of some of those events which have preceded similar events that occurred this year.

As many of us know, it all began in 1965 when IBM announced revolutionary System/360 (S/360) processors and along with that announcement, an operating system to run on the smaller models of those processors. This new operating system was named Disk Operating System/360 (DO S/360), or as it was more commonly called, DO S (not to be confused with the PC operating system by the same name that came along much later). There are a few of us with gray hair still around who remember installing DO S on 24K and 32K S/360 systems. The DOS supervisor took 6K and the remaining storage was available for program execution. When compared to today’s most current version, z/VSE 4.1, with a supervisor of about 700K and support for up to 8GB of real storage, VSE users can definitely see how much their operating system has evolved and grown to support much larger systems than originally intended.

Each major name change in the VSE operating system was usually related to support of new processors or operating system capability. The announcement of a new version or release of VSE often included discontinuance of support for older technology processors. In 1972, IBM announced System/370 processors and virtual storage. DOS/VS was announced to support that new processor family and its virtual storage capabilities, and customers experienced their first upgrades of hardware and operating systems to exploit new technologies.

In 1979, IBM announced the 4300 family of processors. DO S/VS was replaced by an “extended” version, DO S/VSE, to support these processors and to provide exploitation of the larger, real memory sizes of these systems with more partitions and virtual storage capabilities. The processor and VSE operating system evolution continued in 1986 with the announcement of the 9370 line of processors and VSE/Systems Package (VSE/SP). In the early ’80s, S/370-XA (eXtended Architecture) was announced. This provided 31-bit support capabilities for MVS and VM systems; however, VSE/SP supported only S/370 24-bit (16MB) architecture.

In 1990, VSE/SP became VSE/ESA. This was the first VSE release to support Extended System Architecture/390 (ESA/390) and System/390 processors such as the 9021, 9121, and 9221 processors introduced with the ES/9000 processor family. VSE was extended to support 31-bit real and virtual addressing. VSE/ ESA also still supported the ESA/370 mode and 370-mode of the earlier processors that VSE/SP Version 4 supported, except for the System/370 135 and 138 models. This new VSE version allowed customers to move to newer supported levels of the operating system without having to do a processor upgrade.

In 1994, IBM announced CMO S technology with the first generation of the S/390 Parallel Enterprise Server processor family or 9672. Several other generations followed along with the Multiprise 2000 processors for smaller users. Version 2 of VSE/ESA was announced in support of these new systems. The new turbo-dispatcher in this version allowed VSE to support and exploit multi-processors. Support for 370-mode processors was discontinued; thus, VSE/ESA V2 no longer ran on 9370, 4341, 4361, or selected 4381 processor models so customers on these systems had to eventually upgrade to new processors to remain on a supported VSE version.

VSE/ESA Version 2.4 was announced in 1998 and supported ESA/390 mode only. This included support for all the 9672 processors, ESA/390-capable ES9000 models, and the Multiprise 2000 processors, which were succeeded by the Multiprise 3000 the following year. VSE/ESA Version 2.4 dropped support for ESA/370 mode, so ESA/370 mode processors, such as the ES/3090 E/J/S models and ESA/370 mode 4381 models, were no longer supported and customers with those processors had to upgrade to ESA/390-capable systems to stay on current VSE releases.

VSE/ESA also was supported on some new entry-level systems that were introduced during this timeframe to replace smaller 4300 and 9370 systems. These were the PC Server 390 (P/390), R/390, and S/390 Integrated Server, which gave those customers who were still running on the older hardware with unsupported VSE releases an economical solution to upgrade their hardware and VSE software to supported levels. Many of these were later replaced by the FLEX/ES solution from Fundamental Software, Inc. This solution enabled emulation of S/390 architecture on Intel-based servers and provided another economical upgrade solution for smaller VSE customers.

2 Pages