Mainframe Master Innovations

Chapter 3

Mainframe Software


Milt Rosberg, global VP for sales marketing and business development for Vanguard Integrity Professionals, talks with Reg Harbeck, M.A., about the company's history and its continuing leadership in mainframe security.


Before electronic computing, the functions of calculating devices were built into their structures and distinct from the data they handled. Then John von Neumann described the stored program concept in which computer programs were merely a kind of data, just as the first electronic computers were being developed. Software was born.

For nearly two decades after this insight, the tension between hardware specifics and software generics led to constant rewriting of software whenever new hardware came along. Mitigated by the arrival of compiled languages, such as COBOL in 1960, soon only platform-specific features needed to be taken into account when a source-code-based program in COBOL or some other language had to be modified for new hardware.


Then, with IBM’s commitment to compatibility between System/360 models and their successors, right through today’s z16 running z/OS and beyond, the mandate for constant rewriting came to an end–at least on the mainframe. Not so much on other platforms that lack this commitment, as Walle illustrates, “Have you ever updated a Windows machine or something to put a fix on? And all of a sudden, you’re updating your whole platform and you’ve got to sit there and wait while the whole thing updates. Well, we don’t do that in z/OS.”


Over the years, an approximate division has emerged in software on the mainframe and other platforms, with the OS and closely related software at a foundational layer, then the middleware that handles everything from security and automation to databases and networking and utilities, and on top of that the application layer. These first two layers were originally perceived almost as extensions of the hardware, while the applications and their customers were a platform’s raison d’être. 


But by the 1970s a distinct software industry began to emerge, offering new solutions, and also competitive alternatives to the default solutions that IBM had originally included with the platform but was now pricing separately.


While applications could build on past successes without gratuitous rewrites, thanks to IBM’s promise and to compiled languages, the middleware had to be more sensitive to changes in context in order to be compatible with the latest innovations on the platform. And the momentum of innovation on the mainframe only ever increased. 


For ISVs this was challenging enough, but IBM had given itself an even greater challenge: their software had to retain integrity with previous versions just like their mainframe hardware had to stay compatible across generations.


“Working with software upgrade and compatibility, this promise is always forefront of my mind every single day,” Walle says.


“So in order to keep software current in customer shops, we really have to be stringent about workload compatibility because the workload that you’ve already invested those 50 years in, you want to still be able to run today and you want to be able to have it scream on today’s new hardware. So, in order to make that we need to be looking at compatibility all the time. And this is something that is unique to z/OS.


“We spend a lot of time in development, making sure that everything we do is compatible so that new software can come into the customer shop that much faster to help them stay current and they spend less time doing upgrades and more time finding new value, putting new functions in getting them to work. So, we try to constantly work on this compatibility issue within development.


“But it’s kind of a two-edged sword because we want to put new stuff in and yet we have to make sure that the old stuff way runs the same way that it did or as close as possible to the way it used to run very transparently to the workload. So, it’s a huge strength that we have on z/OS because on other platforms, when you upgrade, you might even have to change applications. And that’s just crazy. We don’t do that in z/OS, right? So, this is why it makes z/OS very different, very unique and why we just work very hard to make up our compatibility part of the platform.”


As a consequence, a persistent and essential trait of the IBM mainframe hardware and software is integrity, which is a foundational aspect of the security of the platform.