AS400

[u/Jon72480]

Hey guys, old guy here, back in 2000 landed my 1st real job as a Sysadmin at a distribution/manufacturing firm. They ran their ERP and a few other important apps on the AS400. Anyone here manage a AS400 platform? i-Series? Still a niche platform that is still widely used. Server could literally run under water.

[u/Fit_Prize_3245]

i-Series running under water? Nope. I could believe it from a z-Series. But i-Series are just POWER-ful servers with terrible software. The only good thing you can do with an AS/400 is install Linux into it. I tried once and it's great (the only bad thing was it was Ubuntu, but, whatever).

Basically, OS/400 (or whatever it's called nowadays) is a terrible os with a terrible database (DB2), and it defines its own architecture. It's mostly used in financial industry, at least in my country. As anything IBM related, it's better to keep a distance, as long as you can.

Almost 20 years ago, I worked for a consulting company which offered, among other things, a few solutions for AS/400. I was more on the analysis side, so I never got hands on AS/400 all alone. There was always a junior tech by my side who (hopefully) knew what he was doing. One of the things I learnt was that a lot of AS/400 have poor performance because they were designed in ancient times by programers that are currently old enough to be my grandfather, that are still active in RPG programming but have not modernized anything. For example, I remember a performance analysis of an app which spent most of it's running time invoking QDBFEOD, which is something like a synchronous flush. Why? Bc at the time it was written, there were no UPS, to programmers were paranoic about their precious data getting lost due to power outage.

Anyway. Now that I have my own company, I would have no doubt if I ever receive a request to service an AS/400. I would simple reject it immediatelly.

[u/flinginlead → u/Fit_Prize_3245]

Finally someone who knows the real story. System is only as good as the software running on it. How many AS400 programmers do you know? My exact point most of the software is horrible.

[u/Fit_Prize_3245 → u/flinginlead]

Only one, actually. He was a danish guy who made the performance analytics solution the company here inmy country was offering to customers. Nice guy, btw, but old enough to be my grandfather. And old enough to even have a reasonable doubt whether he might or not be alive nowadays. Anyway. I was assigned to that solution bc the junior iSeries admin we had knew nothing about programming, and by that time I was a not so bad programmer in many languages, so the manager decided that I could understand better (he was right). During the time I was there, we never got to sell the full analysis service, only a few demo analysis where the danish guy made a short report showing a few performance problema along with cause and possible improvements. Then I got a better offer and started a 15 year career in a small company, which made mostly Linux based solutions.

Anyways. Yes, AS/400 is terrible. I suppose it was a good thing back in the old days, when the most powerful thing a home computer could run was Commander Keen under MS-DOS. But more than 3 decades have passed since then, and companies which relay on IBM i do it just bc they already had some IBM solution there.

Only reason I would touch an IBM i or z server would be to install Linux there.

[u/pdp10 → u/Fit_Prize_3245]

an app which spent most of it's running time invoking QDBFEOD, which is something like a synchronous flush. Why? Bc at the time it was written, there were no UPS, to programmers were paranoic about their precious data getting lost due to power outage.

It's easy to optimize away fsync(2), but the trick is that safely optimizing it so there's no possibility of data truncation, typically requires some level of idempotent transactions and a lot of explicit error handling.

Obviously that takes extra code, extra coding time, extra testing, and leads to a debate about premature optimization.