z/VSE is built on a heritage of ongoing refinement and innovation that spans four decades. This article includes a brief history of VSE. To the many seasoned VSE veterans with years of experience and many memories, I apologize for leaving out so much. To the VSE newcomers, some of whom may not yet be 40 years old, I apologize for including so much.
Disclaimer: The facts contained here have been checked and rechecked. However, 40 years is a very long time and memories fade. There’s no guarantee the author’s memory is correct in every aspect of the last 40 years. Indeed, the reader may remember things differently. That doesn’t necessarily imply that either view of the past is wrong.
1960s
At the beginning of the ’60s, mid-size IBM customers might have used one of two technologies: One option was “unit record” technology. Punched card processing involved transfer of information to punched cards and manual card handling along with sorting, merging, reporting, and summarization using electromechanical unit record equipment. Many early S/360 systems simply automated these legacy unit record applications. Some of those applications may still be running today.
A second option was the IBM 1401 system. The all-transistorized 1401 was the first IBM computer designed for the “mid-market.” The 1401 was quite successful, and 1401 emulation was an important option for many early S/360 customers. Who knows? Some 1401 programs may still be running in 2005.
In 1964, IBM introduced a revolutionary family of computers that offered customers a wide range of compatible processors and common I/O peripherals. By today’s standards, the capacity of even the largest S/360 system was feeble. Nevertheless, by the standards of the late ’60s, the S/360 was an absolute marvel of advanced design and technology.
Fortune magazine famously called the S/360 a $5 billion (U.S.) gamble. If one assumes $1 (U.S.) in 1965 is worth more than $6 (U.S.) today, that means it might be described as a $30 billion (U.S.) gamble in 2005. It was an extraordinary expression of confidence. The task merely involved concurrently designing a comprehensive, enduring, and extendable architecture; designing and building factories to produce and test state-of-the-art components; designing and building factories to produce and test a family of processors and related I/O products; designing, creating, and testing a new operating system, along with key components and utilities; plus hiring and training a new sales and support organization and doing it all while coordinating activities and resources on a worldwide basis at a time before the easy availability of cheap, high bandwidth communications. I am impressed.
The operating system planned for the S/360 was “Operating System/360,” or OS/360. IBM was apparently too busy in those days to give much thought to creative naming. Later, at some point in the development cycle, IBM realized OS/360 would not fit in the limited memory available on entry models. Since the S/360-30 offered ferrite core memory in the range of 16 to 64KB, an alternative to OS/360 was needed.
IBM Endicott developed an alternative operating system designed for smaller members of the S/360 family. The first “VSE” was Disk Operating System/360 (DOS/360). DOS/360 first shipped in 1965. It began with a single partition, but quickly grew to three partitions for basic multi-programming. Later, BTAM added primitive telecommunications. IBM’s belief was that DOS/360 would cover the entry level for just a few years and then somehow fade away as users moved up to OS/360.
In retrospect it may be difficult to understand that assumption. It must be one of those “it seemed to make sense at the time” things. Clearly, VSE didn’t simply fade away. Instead, 40 years later we are celebrating the contributions VSE has made in the past, continues to make in the present, and is likely to make in the future of IT. z/VSE is a tribute to DOS/360. Even more important, z/VSE is a salute to the thousands of exceptional IBM customers who depend on VSE for robust, cost-effective IT solutions.
1970s
IBM followed the success of S/360 by introducing S/370 in 1970. Virtual storage was added in 1972. Virtual storage expanded system capacity and made programming easier and more productive. Real memory options grew as monolithic memory technology replaced ferrite core. Real memory options for the S/370-135 ranged from 96KB to 256KB. In disk storage, the IBM 3330 (100MB per removable pack in early models) replaced older 2311 and 2314 technology.
After 27 releases, DOS/360 became DOS/VS. DOS/VS offered five partitions (later seven) and a relocating loader for effective multi-programming. POWER (Priority Output Writers, Execution Processors, and Input Readers) was added for I/O spooling. One can only imagine how long it took to come up with that acronym. A new VSAM file system for balanced random and sequential processing became part of DOS/VS. Database/Data Communication (DBDC) became a fundamental part of VSE as the use of CICS grew. A hierarchical database known as DL/1 was available as well. At this time, DOS/VS became something we would clearly recognize today as a VSE system.
After a brief partial detour to the Netherlands, responsibility for the VSE system was consolidated at the IBM lab in Boeblingen, Germany.
Starting in the mid-70s, some VSE customers introduced VM to supplement the capabilities of their basic VSE environment. With the introduction of the S/370-138, an update of the basic 135 design, IBM began to implement selected “VM assists” in processor microcode. The assists were designed to reduce the “overhead” of VM. The effect was startling. Once the performance of VSE under VM became “acceptable,” many VSE customers began to exploit VM. They added multiple VSE guests for more processing capacity than a single VSE guest, separated production and test guests to increase system integrity and improve staff productivity, and used CMS as their preferred interactive tool. In 2005, many VSE users continue to exploit the world-class virtualization technology of z/VM. In fact, the unsurpassed ability of z/VM V5 to run and manage multiple Linux guests adds new relevance to VM for many VSE customers.
In 1979, IBM introduced the IBM 4300 system with Large Scale Integration (LSI) logic and solid-state memory based on an advanced 64K bit chip. Real memory options ranged from 512KB to 4,096KB (4MB). Integrated adapters lowered overall hardware costs. Along with the 4300, IBM introduced new disk systems based on Fixed Block Architecture (FBA).
DOS/VS became DOS/VSE. E stood for “extended,” or perhaps “e Series” (the internal code name for the 4300). DOS/VSE offered up to 12 partitions. MSHP was added to enhance service and control of the system. ICCF became the interactive component. ICCF was based on ETSS, a “field-developed” program commonly used at the time. DOS/VSE also offered improvements such as ASI procedures, missing interrupt handler, DASD sharing, etc. ACF/VTAM became a component of VSE. A major extension was support for FBA disk devices. During this period, the practice of charging for IBM software became widespread.
1980s
In 1983, IBM 4361 and 4381 systems added new growth opportunities to the 4300 family (joining the 4331 and 4341).
In 1986, IBM announced the IBM 9370 family of mid-size systems. The 9370 was designed to operate in an office environment and introduced a new form factor for mainframes. The 9370 was packaged for standard 19-inch racks. Four models were included in the initial announcement. Main memory ranged from 4MB to 16MB. In addition to the CPU itself, new rack-mounted FBA disk (IBM 9332 and 9335) and tape (IBM 9347) products were introduced as well.
Slowly and deliberately, DOS/VSE transformed into VSE/Systems Package (VSE/SP). VSE/SP consisted of an integrated, pre-packaged VSE system. The metamorphosis began with the “SIPO” concept. SIPO originated in IBM Canada and was a visionary attempt to provide a pre-configured system. SSX/VSE took integration even further and added a set of systems management dialogs. SSX ultimately proved to be too rigid for most customers. However, the basic approach proved sound. VSE/SP V1 and V2 refined the concept and made it more generally acceptable. The Fast Service Upgrade (FSU) process made release-to-release migration simpler.
By 1987, VSE/SP V3 implemented a packaging concept that remains visible to this day in z/VSE. The structure consists of base and optional products. The “base” is an integrated package containing key, commonly used products. It is designed, developed, tested, delivered, and serviced as an integrated whole. “Optional” products are coordinated so the list contains the correct level of each product. Installation procedures and dialogs are provided. Following an order, base and optional products are stacked together on the delivery media. Service is coordinated for both base and optional products and appropriate prerequisite and corequisite levels and service are identified.
The goal of the packaging was a system with better quality and more stability, and one that was easier to install and service than before. VSE customers approved, and the structure survives today. For example, z/VSE V3.1 base components include the supervisor, dialogs, POWER, VSAM, ICCF, LE, utilities, VSE connectors, HLASM, CICS TS VSE/ESA, ACF/VTAM, TCP/IP for VSE/ESA, DITTO, and DB2. Indeed, MVS adopted a similar approach to transform itself into OS/390 (now z/OS).
VSE/SP V3 also offered major enhancements, including some first introduced in VSE/SP V2. For example, VSE/SP V3 included a new librarian, conditional JCL, and Virtual Address Extensions (VAE). VAE was an attempt to extend the capacity of VSE. It provided up to three address spaces, each with no more that 16MB. Each address space contained all common and shared space. During this period, IBM moved toward a capacity-based software pricing model.
Tape processing declined. Tapes were largely used for backup, archiving, and data interchange. With the IBM 3480, self-contained, easy-to-handle cartridges (“square” tape) replaced traditional reel-to-reel (“round” tape) media.
During the ’80s, some customer applications began to bump up against the limitations of the S/370 24-bit (16MB) architecture. S/370-XA (eXtended Architecture) extensions added 31-bit (2GB) real and virtual addressing in response to customer needs. Because VSE/SP didn’t implement 370-XA architecture, it began to look as if VSE might be left behind.
1990s
The ES/9000 was announced in September 1990. The ES/9000 family included three design points: a rack-mounted ES/9221, an air-cooled ES/9121, and a water-cooled ES/9021. ES/9000 processors implemented Enterprise Systems Architecture (ESA), an extension of 370-XA.
To the delight of VSE customers, VSE experienced a major revitalization in the ’90s. VSE/SP became VSE/ESA Version 1. VSE/ESA V1 kept the best parts of VSE/SP and focused on quality, capacity, and MVS “affinity.”
For increased capacity, VSE/ESA V1 first implemented 31-bit for real memory, then added 31-bit virtual addressing. VSE/ESA V1 offered dynamic partitions (limited by available tasks). VSE/ESA V1 offered Virtual Storage Constraint Relief (VSCR) by moving ACF/VTAM and POWER out of shared partitions. It introduced dynamic channels (the XA channel subsystem), ESCON channels, and up to 1,024 devices for added I/O bandwidth. In later releases, VSE/ESA V1 added support for ESA data spaces and Virtual Disk in storage. VSE/ESA V1 exploited ESA access registers. New versions of CICS/VSE, ACF/VTAM, and VS COBOL II were added for greater MVS affinity.
The lab began to work closely with Independent Software Vendors (ISVs). Prior to VSE/ESA, ISVs had to wait like everyone else until General Availability. Only then could they adapt their own products to the latest VSE release. The result was that few customers could exploit the latest release of VSE until the ISVs changed their products. The delay served no one’s interest. The practice is now to involve ISVs as soon as possible. ISVs have early access to VSE plans, design specifications, and code.
VSE/ESA V1 also established itself in distributed processing. Distributed capabilities, many of which were first introduced in VSE/SP V4, allowed VSE systems to be managed from a central location. During the ’90s, several large IBM customers managed enormous numbers of remote VSE Micro-Channel/370 (9371) systems. However, this proved to be a temporary “niche.” For some customers, consolidated, centralized solutions replaced distributed ones. For others, newer network technology replaced the comparatively rigid, centrally managed approach.
In 1994, after many “experts” had declared “big iron” dead, IBM boldly reinvented the mainframe. At the time, the fastest systems used bipolar semiconductor technology. Unfortunately, bipolar was expensive and used a great deal of power (more heat). Large mainframe systems based on bipolar technology often required large water-cooling units.
The alternative technology, CMOS, was comparatively slow (at the time), but used less electricity (less heat). In addition, since it was more widely used, CMOS components were cheaper to design and build. IBM was confident that CMOS technology would advance quickly and eventually surpass bipolar. The decision turned out to be the right one. In 2005, the most powerful zSeries servers (the z990) are based on CMOS.
The IBM S/390 Parallel Enterprise Server G1 was introduced in 1994. More powerful S/390 CMOS models quickly followed. S/390 Servers also featured an Open Systems Adapter (OSA) for fast, economical network connectivity.
To exploit IBM’s CMOS servers, VSE/ESA V2 replaced V1 in 1994. VSE/ESA V2 introduced the Turbo dispatcher. For the first time, VSE supported n-way servers. VSE/ESA V2 also introduced Language Environment technology and newer levels of COBOL, PL/1, and C for increased MVS affinity. ACF/VTAM V4.2 was added as well.
IBM also used S/390 CMOS technology to create systems designed for smaller customers. For example, in 1996, the IBM S/390 Multiprise 2000 offered up to five processors (CPs), up to 288GB internal disk (using 3380/3390 ECKD format), and OSA adapters. The Multiprise 2000 was a good match for many VSE customers.
VSE/ESA V2.2 shipped in late 1996. It was the first VSE to be “Year 2000” ready.
The Year 2000 “problem” had its origins in the early days of S/360 when memory was a precious resource and 2000 seemed far in the future. Wide-spread practice was to store and process only the last two digits of the year. For example, “1972” was stored as “72,” “1996” was “96,” and “2000” was “00.” As 2000 approached, systems and business applications were exposed. For example, subtracting 72 from 96, the correct answer is 24. However, subtracting 72 from 00, the answer is negative 72 (mathematically OK, but incorrect for its intended use). This simple, seemingly trivial mistake had the potential to seriously disrupt both the financial integrity and the operational effectiveness of many companies.
During this period, TCP/IP became the de facto standard for networking. In 1997, VSE/ESA V2.3 introduced a native TCP/IP (licensed from Connectivity Systems Inc.) implementation.
VSE/ESA V2.4 launched CICS Transaction Server for VSE/ESA (although CICS/VSE continued to ship along with CICS TS VSE/ESA for compatibility reasons). Because CICS TS VSE/ESA was built on the same code base as the equivalent MVS product, it represented a major expansion of MVS affinity.
Many VSE customers spent the last years of the ’90s enabling their systems and applications to be Year 2000 ready.
2000s
In late 1999, the S/390 Multiprise 3000 (based on G5 technology) replaced the earlier Multiprise 2000. The Multiprise 3000 offered one or two processors (the second processor could be configured as either a CP or as an Integrated Facility for Linux [IFL]) and up to 216GB internal disk (with 3380/3390 ECKD format) in a single frame. The Multiprise 3000 was popular among VSE customers. In fact, at the time of this writing (early 2005), many VSE customers still have these systems installed.
In late 1999, IBM also introduced the innovative IBM TotalStorage Enterprise Storage Server (also known as Shark). With fast channels and large cache memory, ESS yielded superb I/O performance. ESS delivered impressive capacity and scalability as well. The ESS design featured redundant components and RAID options for high availability. Finally, advanced copy features such as FlashCopy and Peer-to-Peer Remote Copy (PPRC) helped improve operations. Shark set a new standard in mainframe disk storage.
On New Year’s Eve 1999, the lab had extra staff available to handle whatever emergencies might arise as midnight on Jan. 1, 2000 began in the Pacific and then circled the globe. The critical moment came and went. Nothing much happened. After a while, the extra staff simply went home to their families. Apparently, customer efforts in the last years of the ’90s actually worked.
In the early 2000s, IBM introduced the eServer zSeries 900 and 800 mainframes. Later, the z990 (2003) and z890 (2004) were added to the zSeries family. zSeries servers offer ESCON, FICON, and Fiber Channel Protocol (FCP) channels.
The z890 is the latest in a distinguished line of VSE mainframes. The z890 offers up to four processors and 28 capacity settings, along with 8 to 32GB main memory. Each processor can be either a CP or an IFL. For a more detailed description of the z890, I suggest you read the related article on VSE mainframes.
In 2000, few customers had VSE and nothing else. Most have several kinds of server platforms installed. Hybrid applications (involving one or more platforms) use data and/or processing logic from a number of local or remote platforms. As a result, interoperability between VSE and other commonly used platforms became a key requirement.
With the introduction of VSE/ESA V2.5 in 2000, VSE added interoperability to the VSE objectives of quality, capacity, and z/OS affinity. VSE/ESA V2.5 included e-business connectors at no extra charge. These connectors have components that run on VSE plus Java-based components designed to run on another platform. Because they are based on open and industry standards, VSE Connectors allow each VSE customer to construct hybrid solutions using their platform(s) of choice. Hybrid solutions can involve VSE plus Linux on zSeries, VSE plus Linux on xSeries, VSE plus AIX on pSeries, etc.
Linux on zSeries emerged as a serious option for cost-effective, industrial-strength, on demand solutions as well as infrastructure simplification. Some VSE customers began to exploit Linux on zSeries to supplement the capabilities of their basic VSE environment. VSE Connectors and IBM Middleware supply programming interfaces based on open and industry standards. zSeries Hiper-Sockets provide high bandwidth. IFLs can offer robust, low-cost Linux servers. Finally, z/VM brings it all together by providing a flexible and manageable environment for multiple Linux images.
In 2005, VSE/ESA V2 became z/VSE V3. Like z/VM and Linux on zSeries, z/VSE V3.1 supports FCP-SCSI disks. New or enhanced storage support includes IBM TotalStorage 3494 Virtual Tape Server, 3494 Tape Library, plus DS8000 and DS6000 series disk. z/VSE V3.1 also supports new Advanced Copy functions. z/VSE can execute in 31-bit mode only. It doesn’t implement zArchitecture, and specifically doesn’t implement 64-bit mode capabilities. z/VSE is designed to exploit selected features of IBM zSeries hardware. For a more detailed description of z/VSE V3.1 function, I suggest you read the related article on z/VSE content.
Where Does VSE Go From Here?
The vision embraces a robust z/VSE that helps protect customer investments in core VSE applications, a VSE that uses standards to help integrate VSE and the mainframe into the customer’s network, and a VSE that can be extended by exploiting other platforms—including Linux on zSeries. It also includes support for selected IBM eServer zSeries features as well as selected IBM TotalStorage products and features.
For a more detailed view of the future of VSE, I suggest you read the related article on z/VSE strategy. Another option may be to simply wait for the next special z/Journal VSE supplement in 2045.
Disclaimer: This article reflects the current z/VSE strategy. However, IBM reserves the right to change strategies and plans without notice.
For more information on the history of IBM mainframes, visit the IBM Archives at
http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_intro.html.
For more information on the history of IBM storage, visit the IBM archives at
http://www-03.ibm.com/ibm/history/exhibits/storage/storage_intro.html.
For more on the history of IBM S/360, download your copy of “The 360 Revolution” by Chuck Boyer at ftp://ftp.software.ibm.com/eserver/. zseries/misc/bookoffer/download/360revolution_040704.pdf
