Not all types of recovery require the intervention of a DBA. Instance recovery occurs when some type of instance-terminating event occurs, such as a hard crash of the host server, a shutdown abort, or certain Oracle errors. When an instance terminates, the database is in an inconsistent state. The next time the database is started, the SMON process uses the contents of the redo logs to reconstruct the state of the database before the crash and rolls back uncommitted transactions. All database changes after the last recorded checkpoint are applied to datafiles. Instance recovery is completely automatic and doesn't require the intervention of a DBA. We can, however, monitor it when it occurs, from the alert log, as shown in the following screenshot. As a reminder, to view the alert log, we can invoke the adrci from the command line and choose the alert log for the database.
We know that instance recovery has occurred when we see the phrase, Beginning crash recovery...