I worked on AS/400 for quite a while. Really enjoyed it.
Updating old RPG terminal based code to Java web based stuff was interesting. Simple CRUD interfaces port easily.
And once you're running Java stuff on OS/400 it's also easy to port to the linux environment. And from there is just an argument over databases to bye-bye proprietary hardware.
That's my experience too, it's mostly basic CRUD interfaces. People say it's fast but that's because it gives you the most barebones user-hostile interface you could have.
The company paid IBM $100k to upgrade a single server and this shit is locked with licences for cores and memory. It's not even that fast.
The problem is they are too deep in it now but this shit needs to die.
Updating old RPG terminal based code to Java web based stuff was interesting. Simple CRUD interfaces port easily.
And once you're running Java stuff on OS/400 it's also easy to port to the linux environment. And from there is just an argument over databases to bye-bye proprietary hardware.