"The agency sends 180,000 letters and emails, and dispenses $290m, every day. System 204's doing that handily, but has reached the point at which meaningful changes are becoming tricky."
You know what, if it's still ticking along, I'd be tempted to leave the bloody thing exactly where it is. I don't know about the system, if it runs on old antiquated hardware etc, but probably be thinking in terms of upgrading the hardware platform that the current system runs on (perhaps virtualisation, or emulation of the hardware) but try and leave the software itself alone. It's from the 80's, so is it an old Vax system or something?
As usual, Wikipedia has the answer:
Model 204 is a database management system for IBM and compatible mainframe computers, “born” 1965 October 13,:66 and first deployed in 1972. It incorporates a programming language and an environment for application development. Implemented in assembly language for IBM System/360 and its successors, M204 can deal with very large databases and transaction loads of 1000 TPS.
I would have thought IBM would have a migration path for old IBM System/360 stuff. Are they not the undisputed kings of backward compatibility? This would be an interesting project.
I can just imagine the utter chaos that a new system (from the ground up) would bring, though. In fact, I don't even want to think about it!
Edit: There is emulation available: (from the wikipedia page):
Database Programmer's Toolkit is a freeware PC-based emulation.
Haven't turned up any links though.