I worked at a place that had a little mainframe (essentially a large server) from IBM to port some software to. Most of the people didn't know anything about ma

I worked at a place that had a little mainframe (essentially a large server) from IBM to port some software to. Most of the people didn't know anything about mainframes. On a hot day they had an air condition problem in the data center and had to turn off a lot of machines. They tried to turn off the mainframe using the big button, but it just kept running. Then they decided to pull the power plug. System still kept running. It turned out it had an built-in UPS. After some more attempts they finally managed to turn it off.