[nijave]

I think this is still IBMs license model (at least a few years ago). It was explained to me you basically license a certain amount of compute even though the hardware is in your data center and you pay overages if you exceed your licensed throughput.

Since you license a fixed amount, there were projects at the company looking at running batch/non time sensitive jobs on the mainframe since it was effectively free off peak (I guess power cost was trivially compared to licensing).

[mkesper]

You had online jobs during the day and batch at night then. That's why you always had to have one night between. Obviously doesn't work when load is 24/7.