|
In general, backup and recovery refers to the process and procedures used to protecting your Database System like Oracle against data loss and reconstructing the database after any kind of data loss. A backup is a copy of data from your database that can be used to reconstruct that data.
Typically, an Oracle Database Administrator uses both Physical and Logical backups to guarantee the recovery of a database in case of any failures due to physical media failures or to recover from Logical errors in a database. When referring to a backup in the Oracle world most DBA's refer to Physical Backups. What is Oracle Physical Backup ?
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. Physical backups are the foundation of any sound backup and recovery strategy and are critical to protect against data loss. What is Oracle Logical Backup ?
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. Logical backups are a useful supplement to physical backups in many circumstances but are not sufficient protection against data loss without physical backups. Why recover an Oracle Database from a backup ? There are several types of problems that can affect the Database Operations. Most issues after an instance failure typically may require the DBA to restart a database and will not cause loss of data. Typically these errors can be due to Media Failure or User Errors. An Oracle datafile is very vulnerable to a media failure. A media failure is the failure of a read or write operation of a disk file required to run the Oracle Database. This happens due to a physical problem with the disk such as a head crash or due to software issues in the drivers managing the disk subsystem. The appropriate recovery technique following a media failure depends on the files affected and the types of backup available.
User errors occur when, either due to an error in application logic or a manual mis-step, data in your database is changed or deleted incorrectly. Data loss due to user error includes such missteps as dropping important tables or deleting or changing the contents of a table. While user training and careful management of privileges can prevent most user errors, your backup strategy determines how gracefully you recover the lost data when user error does cause data loss.
|
