Instance recovery is recovery of a single database instance. It is also called crash recovery if ur database has only instance.
Crash recovery is recovery of all instances in database.
- Datafile media recovery is used to recover from a lost or damaged current datafile or control file.
- Block media recovery is a technique for restoring and recovering individual data blocks while all database files remain online and available. If corruption is limited to only a few blocks among a subset of database files, then block media recovery may be preferable to datafile recovery.
Crash recovery is used to recover from a failure either when a single-instance database crashes or all instances of an Oracle Real Application Clusters database crashes.