Operators would perform tasks such as arranging to run jobs submitted by users, mounting magnetic tapes and disk packs, and bootstrapping the operating system after the machine crashed, or was powered on.
Operators were generally not programmers, but on a large mainframe they had to know a fair amount - e.g. how to deal with a multi-processor system which had had one of the CPU's fail, which would require:
- recognizing that a CPU failure had occurred
- working out which CPU had failed
- reconfiguring the system so that it would not try to use that CPU