When I worked at a data center for a bank, we had basically the exact setup you are describing. Part of my responsibilities was to take note of the amount that

When I worked at a data center for a bank, we had basically the exact setup you are describing. Part of my responsibilities was to take note of the amount that came through via ACH on that Windows machine (Windows 3.11 actually... this was in 2001) and enter it into a Lotus 1-2-3 spreadsheet, along with totals which I got from reports that ran after the days batch processing completed, and make sure they balanced. If they didn't balance, I had to go hunting and pray that I simply transposed a number or typoed something along the way... if I did not, I honestly don't know what happened. I had to call one of the other employees to come in and orchestrate getting it fixed. (I was alone at the data center, which consisted of a mainframe and a handful of PCs... probably an order of magnitude smaller than what you would picture if I just say 'data center') Luckily, it happened very very rarely. Maybe a handful of times in the 4 years I worked there.