Fast recovery
Fast recovery is an automatic, fault-tolerant feature that the database server executes every time that it moves from offline to quiescent, administration, or online mode. You are not required to take any administrative actions for fast recovery; it is an automatic feature.
The fast-recovery process checks if, the last time that the database server went offline, it did so in uncontrolled conditions. If so, fast recovery returns the database server to a state of physical and logical consistency.
If the fast-recovery process finds that the database server came offline in a controlled manner, the fast-recovery process terminates, and the database server moves to online mode.