Let  us we discuss about backup and recovery  

what is backup and  recovery?

- Backup and recovery is to protect  the database against data loss and reconstruct the database after data loss.

- Backup has been splitted   into two  methods

*Physical backup

*Logical backup  

Physical backup

-Physical backup is a backup of the physical files used  in storing and recovering your database.

-Such as datafiles,control files,archived redo log files

Logical backup

-Logical backup is exporting the logical data(table,tablespace,schemas)  from a database with an Oracle export utility and stored in a binary file.

-Later  we can importing those files to the database corresponding  oracle utility

Backup

Types of failures

*Statement failure

*User error failure

*User process failure (PMON)

*Instance failure (SMON)

*Network failure (Network admin)

*Media failure  

I)Statement failure 

- When a program attempts to enter invalid data into an Oracle Table.

- Proper privileges to perform a task.

II)User error failure

- Abnormal disconnect or performing a terminal program error and losing the session connection.

- BG process rollback the uncommitted transaction  changes to the data and releases the locks.

III)Instance Failure

- Our Database will be shut down due to Hardware , a power failure and an emergency shutdown procedure.

- Check Alert log and trace files. - Just restarting the Database instance using by STARTUP Command.

- Oracle will do an automatic instance or crash recovery at this point.

- Once we restart the db  rolls back the uncommitted transactions from  undo segments and rolls forward to committed changes it in the online redo logs

IV)Network Failure  

Net listener, NIC and network connection has failed.

- DBA must configure the multiple network cards.

( Note: in above failures can be solved once we restart the instance)

V)User Error

- User  deleting  data from table and dropping a table you can use FLASHBACK feature -If the transactions not completed yet, rollback statement.

- Oracle LOGMINER also comes on handy situation like this.

VI)Media Failure

- A media failure is a physical problem with a disk that causes a failure of a read from or write to a disk file that is required to run the database. Any database file can be vulnerable to a media failure. The appropriate recovery technique following a media failure depends on the files affected and the types of backup available.

-Examples of media failure 

i) Head crash

II) File corruption

III)Overwriting or deleting of a datafile.

-Any one of the multiplexed control files are deleted or lost because of disk failure you must restore the missing control file from an existing control file.

-Datafiles, undo table space is deleted or lost because of a disk failure.If you lose one of these files, the instance may shutdown or may not shutdown in such case  

  sql> shutdown abort;           
Then

  sql>startup mount

-Restore the datafiles and recover it.

-An entire redo log group lost. if you have atleast one member of the redo log group , your database instance can continue to operating normally.

-Restore the log file by copying one of  the other members of the same group.

Recovery Solutions
 
reocvery solutions

(source of image:https://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmintro.htm#BRADV99998)

In  above failures can be solved by  RMAN and UMAN method that  work flow has been given that  it