Causes of Instance and media failure in oracle database

There are many failures that occur on database environment . Some of the failures are user error, media failure, instance failure, statement failure and user process failure.

Causes of instance failures:

• When a power outage occurs.
• When hardware failure (CPU failure, memory corruption or OS crush)
• When One of the oracle server background process experiences failure.

And No recovery action needs to be performed by DBA. All redo information is ready by SMON. To restore from this type of failure, start the database.

Phases of instance recovery:
1.Data files out-of-synch
2.Roll forward(redo)
3.committed and uncommitted data in files
4.Rollback (UNDO)
5.Committed data in files
6.Synchronized data files

Causes of Media failures:

• Head crush on a disk drive
• Physical problem in reading from or writing to data files
• File was accidentally erase