“Unless a crisis situation already exists, no IT manager would ever permit system maintenance to occur in a window where they could potentially impact the end user. This “upgrade” should have been performed the moment they shut down Friday after providing enough time for testing and/or recovery before restarting Monday.”
I worked for a large medical corporation in IT for many years. We had a completely separate system for testing, several in fact.
Smart practice. Generally we see different environemts for development, unit testing and QA before a product goes gold and makes it into prod.
Otoh, this sounded like,( and who really knows) they did production maintenance work in prod during the business week.