Google’s book Site Reliability Engineering tells engineers what to do in a major outage: “Your first response in a major outage may be to start troubleshooting and try to find a root cause as quickly as possible. Ignore that instinct!” Instead, “your course of action should be to make the system work as well as it can under the circumstances.” The chapter adds: “Stopping the bleeding should be your first priority.”
The book takes its model from aviation: “Novice pilots are taught that their first responsibility in an emergency is to fly the airplane.” The search for the cause comes afterward, and engineers are told to keep evidence such as logs for it.