The Mainframe

The mainframe was initially an IBM 360 that was later upgraded to an IBM 370. There was a mainIBM 370 console that displayed the different queues. There was the input job queue, the output punch card queue, the print queue, tape queue and disk mount queue. The mainframe had "partitions" of different sizes in which programs would run. You might have two or three small partitions for student programs, one or two medium partitions for larger programs typically run by various facility and one large partition for the occasional large program. One of the jobs of the primary operator was to adjust the size and number of the different partitions to keep the number of jobs in the input queues down. Say if there got to be 50 or 60 small student programs waiting to be processed you would stop a medium queue, let the current job finish, then split the medium queue into two or three small queues to process more small jobs. The Physics guy's program was so large it would take most of the machine and we had to combine just about all the partitions into one super large partition to run his program.

One interesting thing about the 370 mainframe is that it was water-cooled. The mainframe took up an entire room consisting of eight or ten boxes the size of walk-in refrigerators. One unit was the chilled water distribution and control unit that controlled the chilled water to the other units. One thing you had to make sure of was to turn on the chilled water unit before powering up the mainframe. There was one weekend I came into work and the "senior" operator had got there a few minutes before me and she powered up the mainframe but forgetting to turn on the water chiller control unit. Well the mainframe ran for about fifteen minutes when alarms started to go off and the system shut down. We called in the IBM support engineer and it didn't take him long to find the problem, over heating. It didn't hurt the machine, we turned on the cooler unit and were soon back up.