i met a korean guy who was a programmer for a bank. he was learning how to write the COBOL programming language. all of the bank's software was in COBOL, which is really old, and they were updating it to C, which isn't what I would call cutting edge.
I'm sure its a similar situation at nonghyup, and probably other banks around the world, too. i read an article a long time ago about old programmers coming out of retirement to maintain banking systems. i guess some still use mainframes, which went out of style almost thirty years ago.
anyways, you're lucky that your bank went out on a weekday. imagine being on vacation abroad, or even just in korea, and suddenly having no money. like saturday night when you need to take out money for a cab. a couple of years ago one of my friends' bank cards didn't work, she slept in mc donalds that night.
korea is a really safe place, why not just keep 300,000 in your wallet all the time?
or keep a stash at home?