The list of commands to be avoided if you are unsure of their consequences are too numerous to be listed in this forum. My suggestion would be that no matter who tells you to enter a command or make a change that you are unsure of, make that person explain the consequences of the change. I don't even make changes suggested by my Cisco SE who knows my environment, without grilling him of the consequences of those actions if I'm unsure. They don't mind, and if they do, ask to talk to someone else. If you're not satisfied with the answer, get a second opinion from another engineer. While the TAC is, in my opinion, an excellent organization, they are human and prone to make mistakes. You as the network individual making the changes are ultimately responsible for those changes and the consequences of those changes.
