Recapping a Year of ‘z/OS and Friends’
Joe Gulla reviews his year of mainframe exploration, indexing the 24 articles he wrote on the mainframe's architecture
As I spent 2025 covering a wide scope of IBM Z computing topics for “z/OS and Friends,” my goal for those twice-monthly articles was to be as thorough as reasonably possible. Now, as I put a bow on the series, my goal is to make those 24 articles easy to find and put into context. Over the past year, this series covered the following 12 mainframe topics:
- z/Architecture
- z/OS
- JES 2 and 3
- CICS
- IMS
- Database
- Security
- Networking
- Messaging and Integration
- WebSphere Application Server and HTTP Server
- Programming Language Support
- Compendium of widely used interfaces of z/OS
Covering each of these topics with a two-article treatment, “z/OS and Friends” referenced hundreds of features, products, tools, standards, techniques and processes. If you missed any of these articles, you can find them below.
z/Architecture
Mainframe Architecture Makes All the Difference: Then and Now
This is the first of two “z/OS and Friends” articles on mainframe architecture. The history of mainframe computing has been fascinating to experience and even more interesting to read about. I could never have imagined the engineering that went into mainframes without making a study of it. And today, what is happening is extraordinary in its depth and scope—and frankly, is not encumbered but rather fueled by the needs of the mainframe client base. This dance between the past and the future of the mainframe is my motivation in writing this article.
How IBM z/Architecture Has Evolved to Address Client Needs: Pausing to Appreciate
This is the second of two articles on mainframe architecture. 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.
z/OS
A Rich Heritage of Built-in Functions, From Nucleus to Networking
In my 40-plus years as a mainframer, I had never studied an operating system at the elemental level—until now. I hope the results of this inquiry make for an interesting compendium of what is built-in and what is optional.
Optional Features Complete a Compelling and Function-Rich Legacy OS
I am thrilled I took on the challenge to cover z/OS optional features after breaking down its built-in functions, because the information I discovered through this systematic exercise was both interesting and surprising.
JES 2 and 3
JES—One of the Most Important Base Elements of z/OS
Early in my programming career, I didn’t know about the Job Entry Subsystem (JES). Never heard of it and never created my own Job Control Language (JCL). When I discovered JES and became a JCL wizard, I immediately appreciated two things about it.
What Is the JES Programming Dimension and Why Is it Important?
This is the second article in this two-part series on JES. The first part introduced the operational aspect of JES2, and this article continues the discussion with the programming dimension of JES2. But first, I explain a bit of history.
CICS
CICS Changing With the Times While Serving Longstanding Applications
The Customer Information Control System (CICS) has a long history. You might say it exists in a world of the past, present and future as it embraces new, evolving paradigms. It routinely extends itself through the addition of functional support.
z/OS and Friends: Rich Functionality Is What CICS Is All About—Then and Now
Following up on the introduction to the functional aspect of CICS, this article continues the discussion with a focus of new capability delivered in recent releases.
IMS
I thought that headline would get your attention. How about this—IMS Version 13 demonstrated the ability to process 100,000 transactions a second on a single IMS system. IMS has long had a serious focus on performance both with transaction handling and database processing. In my research, I have found out that over 95% of Fortune 1000 companies use IMS in some capacity. The same is true of all the top five U.S. banks.
IMS Transaction Manager: From Its Moonshot Roots to More Recent Product Enhancements
In the first “z/OS and Friends” article on IMS, the focus was the IMS database component (IMS DB). There is, however, another important component focused on transaction management. In this article, I discuss IMS Transaction Manager (IMS TM), as it is the engine that supports database processing. I will also explore recent enhancements that center on making the most of distributed computing innovations. First, let me share some IMS history.
Database
The Unique Benefits of z/OS-Native Database Systems
This is the first of two “z/OS and Friends” articles on database management systems. I am focused on z/OS because there are families of products, like the Db2 family, that run on different platforms, and because of platform differences, the products consume CPU cycles and utilize memory and storage in different ways. There are many important differences besides consumption patterns.
UNIX on z/OS: A Solid Foundation for an Enterprise-Grade DBMS
The first article in this two-part series was all about Db2. I did my best to find and write about the reason that IBM’s implementation of the relational model on z/OS really matters. I have had a long relationship with Db2. So, before I got into UNIX on z/OS, Linux, hypervisors and databases, I wanted to spend a few paragraphs on my experiences around and about Db2.
Security
Examining IBM z/Architecture Security Features, Layer by Layer
IBM’s z/Architecture and z/OS provide a comprehensive and layered approach to enterprise-grade security, offering features designed to meet the substantial needs of the enterprise community, especially those in highly regulated industries. This article is the first in a two-part series focusing on system and application security across the hardware and software landscape. Here, I concentrate on z/Architecture, which is a way of centering on hardware. In the second article, I turn my attention to software, focusing on z/OS security.
Dissecting z/OS Security Software—Base Elements, Optional Features and Products
Security on enterprise computers is interesting, detailed and, at times, challenging to understand, especially for IT practitioners that are not security specialists. After focusing on z/Architecture with an emphasis on hardware, this article is about security software.
Networking
Networking on z/OS: Something for Every Enterprise
Networking on z/Architecture systems running z/OS is a robust and highly integrated environment. IBM has been working on this for decades, fueled by customer wants and needs, and it shows it. There are many networking choices and approaches to utilize with z/OS in support of enterprise-grade communication. Known for its security and scalability, mainframe networking has a dynamic history that started with what we now consider elementary approaches and protocols.
Today, z/OS on the latest z/Architecture servers encompasses a cumulative software stack that includes most of the history of telecommunications innovations, right up to the present. Networking on z/OS evolved from early protocols to System Network Architecture. Later, TCP/IP was fully embraced and utilized. Today, networking on z/OS is still growing and changing.
A Love Letter to NetView, and Other Networking Management and Monitoring Tools on z/OS
For networking management and monitoring on IBM z/OS systems, several powerful products are available, each tailored to different aspects of mainframe operations. Let me start with IBM Z NetView, which is unique in that it is a network monitoring and management program as well a system automation platform. Both network and z/OS are supported by way of NetView’s extraordinary interfaces, features and functions, including REXX language support.
Messaging and Integration
IBM MQ and Beyond: Messaging and Integration Products Deconstructed
When computer applications started to become distributed, databases on one server and applications on another, there developed a need for ways to share data securely and quickly. The network providing a pathway between the application components (and servers) became very important as well. The IT industry went to work on ways to share data between systems, and messaging became an important tool to exchange data. Other integration techniques were developed as well. APIs emerged to access the application and the data it utilizes, from one system to another. API people call it expose; I use access.
Make a Useful Pilot Project Using This Framework for z/OS Hybrid Integration
In my previous article on messaging and integration, I explained products from IBM that are up to the task of connecting different systems and applications. These products included IBM MQ and IBM App Connect Enterprise (ACE) for z/OS, IBM App Connect, z/OS Connect Enterprise Edition (EE), IBM API Connect and IBM DataPower Gateway. In this article, I dig deeper into the subject by laying out a project framework.
WebSphere Application Server and IBM HTTP Server
Modernizing With Confidence: WebSphere Application Server’s Legacy and Future in IT Infrastructure
IBM WebSphere Application Server (WAS) has had incredible growth over 13 major releases since the initial one in 1998. Today, many thousands of companies are using it globally, taking advantage of incredible functionality that offers developers, team leaders and executives an array of implementation choices.
The Web Server Landscape: Where IBM HTTP Server Fits Into the Broader Web Server Ecosystem
In my previous “Z/OS and Friends” article, I covered WebSphere Application Server (WAS), but WAS doesn’t interact with web browser clients on its own. That’s the job of IBM HTTP Server (IHS), which occupies a special role in z/OS as IBM’s custom-made front-end to WebSphere Application Server (WAS).
Programming Language Support
Beyond Legacy: The Modern Language Ecosystem of z/OS
Language is never stagnant, and programming languages are no exception. For evidence of this, just look at z/OS, which supports a broad and evolving range of programming languages and development environments, spanning both commercial and open-source ecosystems.
Building the Future on z/OS With DevOps, CI/CD and Developer Tooling
Why did it take so long for DevOps to become standard practice? It seems like a no-brainer. But it’s questions like these that make it so fascinating to watch the evolution of software deployment. In the case of DevOps, some organizations realized they were suffering from a lack of an interdisciplinary team, so they began cultivating useful relationships between development and operations. The practice didn’t have a formal name yet; it just made sense.
Widely Used Interfaces of z/OS
Navigating the Core: A Compendium of Traditional z/OS Interfaces
From the beginning of this series, “z/OS and Friends,” I have wanted to create a compendium of widely used interfaces with z/OS. It is a long-standing interest of mine as every OS feature, software product and application development environment is modular and relies on programmed interfaces to communicate and interact. In fact, the whole programming world is modular! Think about it for a few seconds and you are likely to agree with me, as modularity is an understated “holy grail of software” in the world of programming.
The z/OS Interface Ecosystem: Bridging Networks, Security, Automation, and Development
Supplying the IT community with robust and useful interfaces is an awesome challenge. In the early days of mainframe computing, the interfaces were direct with a well-defined scope. You invoked a supervisor service, and when you did it right, your program continued to execute.
Of course, there was error handling for problem situations. You might want to review Chapter 8 in the current z/OS documentation, “Providing recovery,” for error handling. There are familiar pairs—GETMAIN/FREEMAIN, WAIT/POST, OPEN/CLOSE and ENQ/DEQ. I still think of these pairs as Jack and Jill, but programming in BAL was not the stuff of nursery rhymes.
What’s Next?
In June 2026, the “z/OS and Friends” articles will be published as a collection in paper and eBook formats by Alazar Press. The book is distributed by Independent Publishers Group (IPG) of Chicago and will be available online and in bookstores. Please see IPG for more details about the book.