IBM i (OS/400): The Database Operating System That Redefined Computing
IBM i (OS/400) the Database Operating System
IBM i, formerly OS/400, is a unique operating system where the database is built into the kernel, not an add-on. It uses object-based architecture, single-level storage, and the TIMI abstraction layer for unmatched backward compatibility. Despite its power, it's locked to IBM Power hardware, making it an elite system. This article explores its origins, architecture, and the enduring green-screen interface.
The operating system perfectly 'understands' the structure of business data and treats an SQL table like any other native system object.
- rbanffy
The article makes me feel the author doesn’t have a deep understanding of some of the mechanisms. TIMI, iirc, is similar to Java (or Smalltalk) bytecode. I’m not sure it’s translated to native instructions on install or on module load, but the native code is kept so that the compilation doesn’t need to happen again. It’s as if the JVM saved a .nativeclass file when a .class file is loaded (kind of one level lower than what Python does, turning a .py file into a .pyc, or .pyo).
The concept of a flat object space we saw in Smalltalk and Lisps (the “system image”) would be seen again, kind of, in the Newton, the Palm, and, IIRC, in Taligent’s Pink. It’s a shame the IBMi is so poorly documented (in sharp contrast with its Z big brother) that no emulator capable of booting OS/400 images exists.
It’s not that this approach is perfect though - it’s really hard to bootstrap a Smalltalk image from scratch. I assume making an IBMi image without a running IBMi system would be similarly challenging.
- theandrewbailey
> Here we reach a point that is simultaneously the platform’s greatest advantage and heaviest burden. Due to such deep integration with dedicated and expensive hardware, IBM i is an “elite” system, in the less positive sense. A mere mortal, computer science student, or enthusiast has no chance to “touch” this system in the comfort of their home. You cannot download an ISO image from the internet, install it on a virtual machine in VirtualBox, or run it on your laptop. The barrier to entry is set at the price level of an IBM Power server, which effectively cuts off the supply of “fresh blood” and makes knowledge of this fascinating architecture passed down almost like guild knowledge, only within large organizations.
I took a course about these back in college. I thought it would be mind-expanding to see how computing could be outside of conventional Windows/Unix/Linux inspired environments, and use something with a very different design. The instructor had a desktop of one of these in his office. I remember logging into an official IBM educational system with a terminal emulator for an assignment.
Unfortunately, the instructor left about a month in, and I switched to a course involving UML modeling for programming Lego Mindstorm robots. Being hands-on with Mindstorms was cool, but I wonder what could have been had I finished the other course.
- rwmj
I'd recommend people read "Inside the AS400" by Frank G. Soltis, as the concepts behind the OS are quite strange and unlike anything else I've ever seen. Unfortunately paper copies are pretty expensive, but there's a high quality PDF floating around on Bittorrent.
- whartung
I'm curious how much of the AS/400 architecture leaks out to the application developers. In the end, the vast majority of the work done on these machines was done in RPG and COBOL.
Curious if most of the architecture was visible to the actual operators, but the developers themselves were, perhaps, a bit isolated from it all.
Because, I don't think HN is a site for "Unix/NT" enthusiasts, but more so high level "computerists" in general. And I don't think that AS/400 application developers would be any less interested in computing than other developers.
Yet, anecdotally, over the years, as much as I've heard bits and pieces about how interesting the AS/400 system is, I've heard anyone talking it up. How they're able to do Cool Computing Thing because of the OS or architecture that can't readily be done on other systems at the time. How the unique features of the AS/400 solved their application and systems problems.
At my office, long ago, we were looking to replace our entire system, and we actually went to an AS/400 demo. But it was very expensive, and whatever they were selling wasn't really resonating with me as a developer, or my boss as a manager. Always wondered "what if" had we got such a system and had to use it in anger what it would have been like.
Anyone have any war stories to share?
- variodot
IBM i was k8s before k8s, with fewer yaml files and better backwards compat
Some of my first exposure to enterprise IT was via the AS/400 and served as a fantastic basis for the cloud stack and agents of today.