Backup & Recovery

1. Introduction to Backup and Recovery:
    Purpose of Backup and Recovery:
                   As a backup administrator, your principal duty is to devise, implement, and manage a backup and recovery strategy. In general, the purpose of backup and recovery strategy is to protect the database against data loss and reconstruct the database after data loss. Typically, backup administration tasks include:

• Planning and testing responses to different kinds of failures
• Configuring the database environment for backup and recovery
• Setting up a backup schedule
• Monitoring the backup and recovery environment
• Troubleshooting backup problems
• Recovering from data loss if the need arises

As a backup administrator, you may also be asked to perform other duties that are related to backup and recovery:

• Data preservation, which involves creating a database copy for long-term storage
• Data transfer, which involves moving data from one database or one host to another

Data Protection:
          As a backup administrator, your primary job is making and monitoring backups for data protection. A backup is a copy of data of a database that you can use to reconstruct data. A backup can be either a physical backup or a logical backup.
          Physical backups are copies of the physical files used in storing and recovering a database. These files include datafiles, control files, and archived redo logs. Ultimately, every physical backup is a copy of files that store database information to another location, whether on disk or on offline storage media such as tape.
          Logical backups contain logical data such as tables and stored procedures. You can use Oracle Data Pump to export logical data to binary files, which you can later import into the database. the Data Pump command-line clients expdp and impdp use DBMS_DATAPUMPand DBMS_METADATA PL/SQL packages.
           Physical backups are the foundation of any sound backup and recovery strategy. Logical backups are a useful supplement to physical backups in many circumstances but are not sufficient protection against data loss without physical backups.
            Unless otherwise specified, the term backup as used in the backup and recovery documentation refers to a physical backup. Backing up a database is the act of making a physical backup.
             While several problems can halt the normal operation of an Oracle database of affect database I/O operations, only some typically require DBA intervention and data recovery: Media Failure, User Errors, and Application Errors. Other failures may require DBA intervention without causing data or requiring recovery from backup. For example, you need to restart the database after an instance failure or allocate more disk space after statement failure because of a full datafile.