[This is an excerpt from Chapter Six, Basic Troubleshooting]
Think of the job of a police detective assigned to the forensics unit. No matter what time of day or night, when a crime happens they will be called to investigate. They make certain the scene is secure, they gather their evidence, interview witnesses and suspects, and do their best to solve the crime. Not only will they need to interview people but they will need to set up surveillance on their suspects and monitor their activities for a period of time.
On television all of this happens in less than an hour. In real life it takes a little bit longer. And some crimes never get solved.
Now think about your life as a DBA. No matter what time of the day or night someone, somewhere, is going to have an issue with a database or a database server. And when that happens, you are going to get called in to investigate. You will be expected to immediately analyze all available details and provide a recommended course of action. If your job was a television show, you would be given about an hour to solve the issue. In real life people want an answer in less than a few minutes, especially if it is the middle of the night. And rarely are your issues allowed to go unsolved.
In order to provide that high level of support you will need to make certain you can do three things. First, you need to know where to look. Second, you need to know what questions to ask (and who to ask). And third, either review your monitoring or put your monitoring in place. In order to provide that high level of support you will need to make certain you can do three things. First, you need to know where to look, which we will assume to mean an incident has taken place. Second, you need to know what questions to ask (and who to ask), which you can think of as an interview (or an interrogation). And third, either review your monitoring or put your monitoring in place, which is the same as surveillance.
That is the DBA circle of life: something will happen, you will ask some questions, and you need to monitor some things going forward.