Message from SHARE: Virtualizing the Mainframe, 50 Years and Going Strong

By Rick Barlow, SHARE LVM Program Manager

Did you know this year marks 50 years of mainframe virtualization? In fact, the majority of the concepts of virtualization on all platforms began on mainframes. What many mainframers today don’t realize is that they benefit from this long history, even if they are not running virtualization management software such as z/VM. What everyone commonly understands as logical partition management on the machines (LPAR or PR/SM) has its roots in the same VM from the mid-1980s. IBM depends on a customized version of VM to develop and test new releases on all of the mainframe operating systems, including z/OS and z/VSE. Many vendors also depend on VM to test their products. Many VM functions have been provided using Service Virtual Machines, making VM the origin of Client / Server technology.

Over the years, SHARE has played a significant role in the progress of mainframe virtualization. Until 2001, most mainframe software was priced by machine capacity – the faster the machine, the more processing power, the higher the cost. As this cost became prohibitive, several SHARE members met with IBM leadership and, in a cooperative effort, devised a new pricing model, which ultimately made it more affordable and accessible. SHARE members have also been integral in the development of  dynamic features of VM, including both software and hardware reconfiguration. Using VM commands, we have the ability to change the characteristics of I/O devices, dynamically adding memory to the LPAR, or even adding/changing some core control program functions without taking an outage. These were huge improvements and because SHARE has such a broad member base, the input we provide carries a lot of weight. IBM Development teams and SHARE Technical Steering Committee members meet on a regular basis to discuss potential development and enhancements to VM.

So what has mainframe virtualization given to SHARE members? Perhaps one of the greatest advantages is access to the mainframe’s architecture. Unlike software virtualization, virtualization on mainframes is based on a direct architectural replica of the real hardware. In fact, the high performance of virtualization on mainframes is directly related to hardware features that allow each virtual machine image to be dispatched directly on the hardware as if they were the only workload on the machine.

With this kind of power available, we can run isolated test scenarios without interrupting the work of other workload that shares the same physical mainframe. Many system programmers will remember having to run tests at odd hours or on weekends. Thankfully, those days are long gone. What’s more, just before the turn of the millennium, it was mainframe virtualization that allowed my shop to run isolated tests and turn the clocks forward to ensure no fallout would ensue when the calendar flipped. 

There are countless other examples of the benefits of virtualization, including disaster recovery sites that use VM to replicate much larger data centers, as well as the creation of virtual devices to test platform upgrades without access to the actual device (i.e. virtual printer, network device). The last 50 years have brought tremendous progress and innovation, and SHARE’s continued influence in the mainframe space will only take us further. Here’s to the next 50 years being equally, if not more, successful.  

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