1.Categories of Failures
.Statement failure
.User process failure
.user error
.Instance failure
.Media failure
.Network failure

2.Cause of instance Faulure
An instance failure may occur for numerous reasons:
.A power outage occurs that causes the server to become unavailable
.The server becomes unavailable due to hardware problems such as CPU failure,
memory corruption,or an operating system crash
.One of the Oracle server background processes(DBWn,LGWR,PMON,SMON,CKPT)experiences a failure.

3.To recover from instance failure,the DBA:
.Start the instance.The Oracle server will automatically recover,performng both the roll forward and rollback phases.
.Investigates the cause of failure by reading the instance alert.log file and any other trace files
that were generated during the instance failure.

Note:
There may be time delay between starting the database and the “Database opend” notification–
This is the roll forward phase that takes place while the database is mounted.

4.Causes of Media Failures
.The disk drive that held one of the database files experienced a head crash.
.There is a physical problem reading from or writing to the files needed for normal database operation.
.A file was accidentally erased.

5.Resolutions for Media Failures
.The backup method you choose and which files are affected
.The Archivelog mode of operation of the database.If archiving is used,you can apply archived redo log files to
recover committed data since the last backup.

5.Defining a Backup and Recovery Strategy
Some questions to consider when selecting a backup strategy:
.Given the expectation of system availability,dose management understand the tradeoffs of the backup strategy taht is chosen?
.Are there dedicated resources available which will be needed to ensure a successful backup and recovery strategy?
.Is the importance of taking backups are preparing recovery procedures clearly understood?

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