Defstat
A multilevel alert protocol, defstat, or defense statuses, was used to define the operations of all Imperial installations, including the Death Star.
Defstat 0 indicated the normal operation of the station. Defstat 1, only a warning, indicated that the station was on alert, and all defenses were upgraded to operational station. Defstat 2 indicated that an enemy craft had been identified in the space surrounding the craft's position. Defstat 3 was the highest level, indicating that the station was actively engaged in combat.