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This MainframeZone page provides interesting and useful information for IBM mainframe users.

MainframeZone founder, Bob Thomas, has been publishing mainframe-centric magazines since 1986. The titles of these publications have been: 4300 Journal, Mainframe Journal, Enterprise Systems Journal, z/Journal, Enterprise Tech Journal and Enterprise Executive.

09/17/2026

MAINFRAME HISTORY
The mainframe’s most important button — IPL.

Long before anyone talked about “rebooting” a computer, mainframers had another term: IPL — Initial Program Load.

On the IBM System/360, the operator selected the device containing the operating system and initiated the load. The process read the initial program into memory and began bringing the system to life.

Today, IBM defines an IPL of z/OS as loading the operating system from disk into real storage and executing it.

But an IPL wasn’t something operators did casually.

A mainframe was expected to keep running. An IPL meant interrupting production, so it was normally planned carefully — and everybody involved wanted the system to come back cleanly.

Modern z/OS systems are designed to operate continuously, potentially for months between IPLs.

The hardware has changed dramatically.

Today the process can be initiated through the Hardware Management Console rather than a big illuminated console button.

But after more than half a century, mainframers still don’t say: “Reboot it.”

They say: “IPL it.”

09/09/2026

MAINFRAME HISTORY
Why was the mainframe operator so powerful?

There was a time when one of the most powerful people in the data center wasn’t a programmer or the data processing manager: It was the mainframe operator sitting at the console.

The operator monitored the system, started and stopped jobs and system tasks, responded to console messages, controlled peripheral equipment, and could IPL the system. When something went wrong, the mainframe frequently required a human decision.

Experienced operators knew which messages were routine, which jobs could wait, and which problem meant calling the systems programmer at 2:00 in the morning.

Much of that work has since been automated. Today’s mainframes can handle countless situations that once demanded an operator’s immediate attention. But back then, the person at that console carried enormous responsibility.

The mainframe may have run the company — but somebody had to run the mainframe.

09/01/2026

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08/27/2026

MAINFRAME HISTORY
There was a time when you could pick up a company’s database by the handle and walk away with it.

In the 1960s, disk storage wasn’t necessarily sealed permanently inside a computer. IBM’s removable disk packs could be taken out of a drive, covered, carried to a storage area — and another pack installed in their place.

The IBM 1316 Disk Pack contained six 14-inch disks and weighed about 9.4 pounds. Introduced with the IBM 1311 Disk Storage Drive, it could hold about 2 million characters—roughly the equivalent of 25,000 punched cards.

Then came the System/360 era. The IBM 2311 Disk Storage Drive used the same basic removable 1316 pack, but improved recording technology increased its capacity to about 7.25 million bytes.

And IBM kept going. The IBM 2314 Direct Access Storage Facility used the larger 2316 Disk Pack. It contained 11 disks, provided 20 recording surfaces and held about 29.2 million bytes. A 2314 installation could have eight disk packs online at once, with a ninth drive available as a spare.

Today, we routinely carry hundreds of gigabytes, or even terabytes, of storage in something that weighs only a few ounces.

But in the early mainframe era: data had weight, and sometimes, it had a handle.

08/20/2026

The Industry Network Technology Council (INTC) announces the upcoming webinar:

PQC and OpenSSL: Practical Integration and Deployment
Date: August 25, 2026
Time: 15:00 UTC - 16:00 UTC
Register: https://us06web.zoom.us/webinar/register/WN_Utcgy6NSRQyQGBqtu4ju9Q

OpenSSL plays a central role in securing internet communications, making it a critical platform for integrating PQC into real-world systems. As PQC algorithms move toward standardization, support for hybrid and quantum-resistant key exchange and signatures is emerging within OpenSSL and related libraries.

This session explores how PQC is being incorporated into OpenSSL, including provider-based architectures, integration with external libraries such as liboqs, and support for hybrid TLS handshakes.

Attendees will gain practical insight into configuring and testing PQC-enabled OpenSSL environments, including enabling new cipher suites, experimenting with hybrid key exchange groups, and evaluating performance impacts. The session also addresses interoperability, backward compatibility, and deployment challenges.

Rich Salz is a highly respected Internet security architect, software engineer, and standards contributor with decades of experience in applied cryptography, secure communications, and large-scale Internet infrastructure. He has held senior technical roles at Akamai Technologies, IBM, and DataPower, where he helped design and implement security products used across enterprise and Internet environments. Rich is widely recognized for his long-standing contributions to OpenSSL, one of the world’s most widely deployed cryptographic libraries, and has played an important role in advancing secure protocol implementations and operational security practices.

08/16/2026

MAINFRAME HISTORY
When the Mainframe Console Lost Its Lights

For years, the image of a mainframe computer was unmistakable: rows of flashing lights, switches, and push buttons covering the operator’s console.

Then, in 1972, IBM introduced the 370/158 — and much of that suddenly disappeared.

The 370/158’s newly designed console replaced most of those familiar lights and switches with something remarkably modern for its time: a CRT display, keyboard, and light pen.

Instead of flipping switches and watching rows of indicator lights, an operator could point the light pen directly at control characters displayed on the screen to perform console functions.

08/11/2026

MAINFRAME HISTORY
When programmers wrote code on paper.

Long before programmers sat in front of interactive terminals, there was the ubiquitous IBM COBOL Coding Form.

For thousands of COBOL programmers in the 1960s and 1970s, this piece of paper was where a program often began.

The form wasn’t simply lined paper. Its columns corresponded to the 80 columns of an IBM punched card, and COBOL programmers had to pay attention to exactly where they wrote each character.

Columns 1–6 could contain sequence numbers. Column 7 had a special purpose—an asterisk could turn the line into a comment. COBOL statements were written in designated Area A and Area B portions of the form. Columns 73–80 could be used for identification or sequencing.

08/05/2026

MAINFRAME HISTORY
The best-selling IBM mainframe family of all time was unquestionably the IBM System/360, introduced on April 7, 1964.

It completely transformed the computer industry and became the foundation for every IBM mainframe architecture that followed. Within its first month, IBM received more than 1,000 orders — far beyond expectations — and the System/360 went on to dominate the worldwide mainframe market.

Among individual models, the System/360 Model 30 is generally regarded by historians as the best-selling IBM mainframe ever. IBM never published complete shipment figures by model, but industry historians agree that the Model 30 outsold every other System/360 model because it was:

* The lowest-priced member of the System/360 family.
* Ideal for thousands of small and medium-sized businesses.
* Widely adopted by universities, hospitals, manufacturers, and government agencies.
* Available for many years with numerous upgrades.

For perspective, the most significant IBM mainframe families were:

* System/360 (1964) – The best-selling and most influential family ever.
* System/370 (1970) – Also extremely successful, building on the 360 architecture with virtual memory.
* System/390 (1990) – Kept the architecture thriving through the client/server era and the rise of the Internet.
* IBM zSeries / System z / IBM Z (2000–present) – Today’s descendants of the original System/360 architecture.

Although the Model 30 sold in the greatest numbers, the System/360 Model 50 (pictured below) is often remembered as the “sweet spot” of the line because it balanced price and performance so well. Many large commercial data centers standardized on the Model 50 before eventually upgrading to the 65 or 75.

Most mainframers would probably guess the Model 65 or 370/158, but the humble System/360 Model 30 is the machine that introduced an enormous number of organizations to IBM’s compatible architecture.

08/01/2026

MAINFRAME HISTORY
IBM introduced the 370/135 on March 8, 1971. It was developed at the IBM facility at Hursley Park, England. It was manufactured in Kingston, NY, Havant, England, and Jujisawa, Japan. (Coincidentally, the ubiquitous 3270 information display system was announced two days later.)

The first customer shipments of the 370/135 began in April 1972.

The 370/135 was the last System/370 model to be introduced without virtual memory. But it was engineered so it could be later upgraded in the field, producing the 370/135-3.

According to DataPro: "The Model 135 offered a combination of virtues that few buyers of small-to-medium-scale computers could afford to ignore: impressive price/performance, advanced hardware technology, high-performance peripheral equipment, and proven software."

Users of 360/40s were especially attracted to it because it offered significantly higher performance together with modest reductions in equipment costs.

The 370/135 was withdrawn from marketing on October 16, 1979.

07/29/2026

MAINFRAME HISTORY
If you worked in a mainframe data center in the 1960s, 1970s, or 1980s, you probably remember the sound — the 1403 high-speed line printer hammered away hour after hour, producing payroll reports, invoices, inventory listings, financial statements, utility bills, and mountains of green-bar paper.

It rarely stopped.

Operators constantly changed paper, replaced ribbons or print bands, tore apart reports, and stacked thousands of pages for distribution the next morning.

To many mainframers, that rhythmic sound wasn’t noise — it was the sound of business getting done.

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