Mainframes are still in use partly because (until perhaps very recently), they are bar-none when it comes to high-availability and disaster recovery. I did som

Mainframes are still in use partly because (until perhaps very recently), they are bar-none when it comes to high-availability and disaster recovery. I did some work in COBOL on a Unisys mainframe back in the late 90s, and I'm still impressed by that thing. You could walk over, pull the plug on it while it was in the middle of running a payroll job, a finance job, and half a dozen other things. Plug it back in, wait a few minutes, and it would pick up right where it left off. No data corruption, no other hassles. Migrating away from that thing was often discussed, but it would have been a tremendous hassle. For one, there was no simple way to migrate the huge volumes of data off of it; for another, even if you could, decoding it would have been a neat challenge. Then there was the matter of all the years of business logic that, while not pretty, worked with very few problems. ...and this was just for a school district in the East Bay. I can't imagine what it would look like for a big financial company.