Instance recovery in Oracle RAC does not include the recovery of applications that were running on the failed instance. Oracle Clusterware restarts the instance automatically.
Applications that were running on a node before it failed continue running by using failure recognition and recovery. This provides consistent and uninterrupted service if hardware or software fails. When one instance performs recovery for another instance, the surviving instance reads online redo logs generated by the failed instance and uses that information to ensure that committed transactions are recorded in the database. Thus, data from committed transactions is not lost. The instance performing recovery rolls back transactions that were active at the time of the failure and releases resources used by those transactions.
Note:
All online redo logs must be accessible for instance recovery. Therefore, Oracle recommends that you mirror your online redo logs.