Answer to Question #194424 in Databases | SQL | Oracle | MS Access for oliver

Question

What is Backup and Recovery in DBMS? 

Answer 1

A backup is a copy of data from your database that can be used to reconstruct that data. Backups can be divided into physical backups and logical backups.

Physical backups are backups of the physical files used in storing and recovering your database, such as datafiles, control files, and archived redo logs. Ultimately, every physical backup is a copy of files storing database information to some other location, whether on disk or some offline storage such as tape.

Logical backups contain logical data (for example, tables or stored procedures) exported from a database with an Oracle export utility and stored in a binary file, for later re-importing into a database using the corresponding Oracle import utility.

Database recovery is the process of restoring the database to a correct (consistent) state in the event of a failure. In other words, it is the process of restoring the database to the most recent consistent state that existed shortly before the time of system failure. The failure may be the result of a system crash due to hardware or software errors, a media failure such as head crash, or a software error in the application such as a logical error in the program that is accessing the database. Recovery restores a database form a given state, usually inconsistent, to a previously consistent state.