With hindsight it was sure exciting but not really fun. There was huge pressure to get the machine back up again. An outage might mean that an entire bank bran

With hindsight it was sure exciting but not really fun. There was huge pressure to get the machine back up again. An outage might mean that an entire bank branch was down, or that payroll could not be run. The CEO could be looking over your shoulder. That kind of pressure saps the fun quickly. Also the bugs could be very, very hard hard to find. In room-sized machines like 3033 for example, there are many thousands of signal leads (trileads) that were many yards long. A slightly bad connection could cause electrical ringing and highly intermittent errors that were excruciatingly difficult to reproduce, let alone to find and fix. Intermittent errors were common and brutal. You could think you'd fixed it, only to have another crash a few hours later. A common debugging technique was to swap cards around and see if the bug moved. Just doing that often introduced new bugs. In latter years the role of the on-site engineer was reduced, and often you would be a lacky for some remote engineer back in the plant where the machine was built.