Observations from a Long-Time Mainframer
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50 Years of Observations From a Mainframe Long-Time Mainframer Innovations By Ed Hallock y first exposure to the IBM mainframe (MFT and MVT) provided multitasking was in 1975, when I began studies for capabilities. S/370 brought about virtual my B.S. in Computer Science, which storage with the VS/1 and VS/2 operating Mled to my professional career start systems, providing a single virtual address as an MVS and JES3 system programmer space shared by all jobs. When I began my back in 1978. Although I can’t claim to have career, IBM had already introduced the been involved with the mainframe for all of MVS (Multiple Virtual Storage) Operating 50 years, I have seen quite a good portion of System in 1974, which enabled multiple these five decades. address spaces, each with up to a whopping 16 megabytes of virtual storage to run in a 1970s and 1980s multitask environment backed by significantly IBM introduced System/370 (S/370) in 1970 less real storage. as the successor to System/360 (S/360), which Back then, the machine room was an was launched in 1965. S/360 operating systems enormous space of raised floor above running B | Enterprise Executive Enterprise| 2017: Issue Executive 6 | 2017: Issue 6 Figure 1: IBM S/370 Model 168 Operators Console cables to support tape drives, spinning disk dominate the mainframe industry, Amdahl devices (some of which were still manually created plug-compatible machines that mountable!), control units, Central Processing could be used with the same hardware Units (CPUs) and real memory. Our flagship and software as offerings from IBM, system was a water-cooled IBM S/370 model but were more cost-effective. Boasting 168 backed by 8MB of real storage and faster uniprocessors, greater performance supported by a main console that rivaled the characteristics and claiming higher bridge of starship Enterprise (see Figure 1). In reliability, the Amdahl mainframe was addition to the S/370-168, we had a smaller compelling to buyers, who were willing to S/370-158 with 4MB of real storage and a consider alternatives to IBM. much less impressive main console. We also These “orange” boxes accounted for some had an older System/360 tucked in a corner of the small amount of competition “Big running some older legacy applications. Blue” had in that very high-margin computer market segment. It also created a lot of fun Amdahl Challenges IBM competition for me and my fellow system In addition to the three IBM mainframes, programmers to witness between the IBM we had an air-cooled Amdahl 470V/6 system. and Amdahl Field Engineers (FEs), who were Now if you’re not an old-time mainframe placed onsite to resolve any operating system professional, you are probably asking: What was and hardware problems. Amdahl had a great an Amdahl? Amdahl Corp. was an information marketing slogan at the time, “Conserve technology company, which specialized in IBM Water, Buy an Amdahl,” and their real mainframe-compatible computer products and memory, which back in the day we referred was founded in 1970 by Gene Amdahl, a former to as core memory, was actually comprised IBM computer engineer best known as chief of gold core modules! architect of the System/360. Some other interesting innovations In the 1970s, when IBM had come to from Amdahl included a 64KB (that’s Enterprise Executive 2017:| 2017: Issue Issue 6 | 6 Enterprise Executive | C Figure 2: IBM z14: Smaller Than the Console on a S/370 Model 168 not a typo!) high-speed memory cache to Early on, I was exposed to two software enhance performance and Multiple Domain products that were focused on the performance Facility (MDF), which was a virtualization of mainframe systems and little did I know at technology introduced long before IBM’s the time that the companies marketing those PR/SM and LPARs. products would be my future employers and By the early 1990s, Amdahl was suffering a significant part of my career. The first was a losses of several hundred million dollars per company called Whitlow Computer Systems, quarter as a result of declining mainframe which developed a sort-merge replacement sales and was no longer a competitive for the standard IBM-provided, sort-merge challenger to IBM. utility. The product was named SyncSort, and later the company would take the same name, Focus on Performance and focused on optimizing sort performance by Throughput reducing CPU time needed to execute a sort Processor performance and system as well as enhance input and output (I/O) throughput were the number one priorities operations to reduce the elapsed time for batch back in the 70s and 80s. Workloads were still jobs containing sort steps. Remember, much of predominantly batch oriented with online the workload was batch JOBs, so ensuring the systems beginning to emerge. We would take production execution schedules were met and lower priority workloads and force them to saving CPU time costs were critical. execute on the S/370-158, knowing the elapsed The second product was called time would be considerably longer there, but OMEGAMON from Candle Corp., which we didn’t care. The higher priority workloads would become part of IBM in 2004. were sent to the S/370-168 and Amdahl 470 OMEGAMON provided a deep-dive analysis for execution. The focus was on turnaround into the MVS operating system and reported and meeting production schedules. on resource utilization at the system and JOB D | Enterprise Executive Enterprise| 2017: Issue Executive 6 | 2017: Issue 6 level, as well as providing alerts for potential System/360 debuted in the mid-1960s, performance delays and degradation issues. System/370 was launched in 1970 as the It could show CPU and memory utilization, successor to the S/360, but there was no paging rates, I/O activity to each device and it new system announced or delivered in the provided the information in real-time to show 1980s. So, S/390 was a big deal! It had many what was happening right now. hardware improvements, including: OMEGAMON had a “dedicated mode,” which enabled an instance of OMEGAMON • IBM’s first air-cooled processors, a few of to direct its information to a dedicated support which were rack mounted, to go along with console. That instance operated with few some of the larger systems, which remained dependencies on other system resources, so water cooled that it could continue to run and provide • Complementary Metal–Oxide– information even when there were problems Semiconductor (CMOS)-based processor with the system. Our operator’s command technology on some models center had a dedicated OMEGAMON console • ESCON (Enterprise Systems Connection) for each system. I knew the product was fiber optic-based connection to devices valuable when I saw both IBM and Amdahl • Logical Partitions (LPARs) as a standard FEs using it to try and resolve system issues to function prevent an IPL. Back then, the systems simply • Hardware support for 32-bit addressing weren’t as reliable as they are today, IPLs were enabled more than 2GB of real memory frequent and they impacted the overall ability per system. to meet production schedules. Mainframe organizations came to rely heavily on products MVS/ESA was the first operating system like SyncSort and OMEGAMON to provide to include support for Open Edition, which and ensure better performance and throughput. provided an API shell, utilities, support for Throughout the 1970s and 1980s System/370 POSIX and other open-system standards, remained the hardware platform and much enabling UNIX-like applications to run on of the focus was on increasing virtual storage the mainframe. MVS/ESA Open Edition also addressability and access for workloads. The included a hierarchical file system. By the first major change was MVS/XA (Multiple end of 1995, IBM rebranded MVS/ESA to Virtual Storage/Extended Architecture), a OS/390, the predecessor to today’s z/OS, and version of MVS that supported the 370-XA Open Edition was rebranded to Unix System architecture, which expanded addresses from Services. I recall that the 1990s was the period 24 bits to 31 bits, providing a 2-gigabyte of client-server technology, along with the addressable memory area. It also supported a proclamation that the mainframe was dying, 24-bit legacy addressing mode for older 24-bit so IBM focused on client-server standards to applications (i.e., those that stored a 24-bit address this, as well as providing significant address in the lower 24 bits of a 32-bit word architectural and performance improvements. and utilized the upper 8 bits of that word for other purposes) and introduced the concept 2000 and Beyond of “addressing mode” for all of us mainframe Over the past two decades many changes software developers. continued in the mainframe world. IBM branding for all mainframes took on the 1990s name zSeries and in 2006 officially became In 1990, IBM made a major announcement IBM System z, now also referred to simply that introduced the System/390 and MVS/ as IBM Z. The hardware platform and z/OS ESA (Enterprise Systems Architecture). operating system included 64-bit addressing, Enterprise Executive 2017:| 2017: Issue Issue 6 | 6 Enterprise Executive | E Over the past five decades the focus for the mainframe has been on bigger, faster and cheaper processing power. and from its inception z/OS supported tri- Security, encryption, support for JAVA modal addressing (24-bit, 31-bit and 64-bit). and open system technologies, processor A variety of special processors have been virtualization, cloud, co-located operating incorporated in System z, including the systems, machine learning algorithms and System z Integrated Information Processor much more are all part of the mainframe world.