How IBM z/Architecture Has Evolved to Address Client Needs: Pausing to Appreciate
From System/360 to z16, longtime mainframer Joe Gulla examines how the technology behind his chosen platform has changed through the years
Editor’s note: This is the second of two TechChannel articles on mainframe architecture for January 2025, part of a yearlong series titled “z/OS and Friends.”
It’s understandable that the general public might take mainframes for granted—they just do their job, after all, reliably conducting the world’s transactions behind the scenes. But there are also aspects of IBM Z, the brand name IBM uses for all its z/Architecture mainframe computers, that can be overlooked even by those who work with the components of the systems every day.
This could even include the basics, like what “Z” stands for in the first place. For the record, the “Z” stands for zero downtime, which IBM engineers’ approach through spare components capable of hot failovers and operating system software that supports dynamic changes. Basically, IBM has engineered a broad array of hardware and software features that work together to enable a maximum of uptime.
As I wrote in my earlier article, current Z systems are the direct descendants of the System/360, which was announced in 1964, as well as the System/370 systems from the 1970s. Here is a brief, well-written history of the IBM mainframe. It is a useful summary.
Application Compatibility Over the Decades
Many applications written for these early architecture systems can still run unmodified on the newest IBM Z system. However, as you know, applications typically require ongoing maintenance and change. It is significant that today, the software development ecosystem including compilers, utilities and testing tools used to support applications have never been more robust, which eases the burden of change.
There has been much written about the need to modernize the application toolset to take advantage of the many time-saving advancements over the years. IBM Solutions states this objective clearly: “Mainframe application modernization empowers organizations to create agile, cost-effective and scalable solutions by using modern technologies. This approach unlocks new value from existing investments, keeping applications competitive in a rapidly evolving digital landscape.” Makes sense, right? This solutions page explains the options available, including use cases with products.
Motivation for Increases in Address Size
As application software made greater and greater demands on the hardware, IBM reworked the systems to use larger address sizes. The System/360 architecture specified a 24-bit address size when referencing bytes in main storage, providing the machine with up to 16 MB of addressable memory. The architecture was extended in the 1970s to support 31-bit addresses, providing a 2 GB address space. Today’s System/z supports 24-, 31- and 64-bit addresses and provides for accessing a main memory size of 16 EB (exabyte).
The mix of 24-, 31- and 64-bit applications and architecture means that storage constraints can be effectively addressed. Here is a virtual storage constraint relief discussion that explains this in a customer information control system (CICS) context. While today’s address space extends to 16 EB, the physical memory supplied on actual machines is smaller than this, making 64-bit addresses a future-proof engineering achievement.
Once IBM branded its mainframes as zero downtime, it continued to innovate, change and expand its mainframes to the present day. In 2025, IBM is expected to announce its latest branded z17, as written about by Futurum and TheNextPlatform.
z16: the Latest System Z
A look at the latest Z system, z16, can tell you a lot about the state of the systems and the approach IBM uses to make them both the present and future of enterprise computing.
The z16 announcement from April 2022 highlights three main features of the new system that will have relevance to “two thirds of the Fortune 100, 45 of the world’s top 50 banks, 8 of the top 10 insurers, 7 of the top 10 global retailers and 8 out of the top 10 telcos as a highly secured platform for running their most mission critical workloads.” IBM’s z16 announcement quantitively addresses the ongoing aptness of mainframes to today’s workloads. In summary, here are the three main features explained:
- Integrated AI: IBM’s z16 system has an integrated on-chip AI accelerator which provides latency-optimized deduction support. This feature enables clients to analyze transactions, in real time, for mission-critical workloads including credit card, healthcare and financial transactions.
- Future-Proof Security: At present, z/Architecture mainframes have robust security features. IBM z16 has new capabilities that are designed to help protect against near-future threats that might be used to break current encryption technologies. This capability is characterized as “quantum-safe encryption.”
- A More Modern System Z for Hybrid Cloud: With z16, IBM continues making investments in service to expedite open-source technology on Z Systems and establish a shared developer experience across hybrid cloud environments.
Varying Areas of Interest
People with different jobs in the buyer community have different interests in the features provided. For instance, people focused on power consumption would be interested in energy efficiency. Consolidating Linux workloads on five IBM z16 systems can reduce energy consumption by 75% and CO2 emissions by over 850 metric tons annually.
Those more focused on security enhancements would be interested in multifactor authentication, data encryption and compliance certifications to safeguard sensitive information. The IBM Z Security and Compliance Center offers an opportunity to simplify and accelerate compliance efforts to reduce costs and enhance staff productivity.
Or, high availability may be the focus. z16 helps ensure continuous operation with minimal downtime, providing reliable performance. Additionally, with IBM Flexible Capacity for Cyber Resiliency, users can manage capacity across locations and transfer workloads on demand. This makes it possible to proactively avoid service disruptions.
Others in a given organization may be primarily focused on the z16 configuration. These individuals look closely at maximum number of engines (200 in the multiframe z16-A01), maximum number of IO drawers (12 in the A01) and maximum memory (40 TB in the A01). All these features reflect increased capacity over the previous release. More details on energy efficiency through configuration enhancements can be found the Configurations section of this product description page.
Timely and Robust
IBM z16 is the latest in a long line of mainframe architectures that have been developed over six decades. The updated architecture is balanced across many areas of client focus—AI, security, open source, energy savings and configuration updates with increase capacity. It remains a remarkable platform to follow, a technological Mount Everest. Spend a few minutes with this “Principles of Operation” document and tell me it doesn’t fill you with wonder.
Next month, I’ll write about z/OS in two parts. First, I’ll focus on its comprehensive base elements, like the Base Control Program, language support, device support, security, management, access methods and networking. Then, I’ll write about data management, protecting and monitor/manage/control with optional features like DFSMSdss, Resource Access Control Facility, and the System Display and Search Facility.