Oracle Backup and Recovery

A backup is a copy of data from your database that can be used to reconstruct that data.  There are two types of Backup:

Logical Backup

• The logical backup technique uses the IMPORT/EXPORT utilities to create the
  backup copy of the database.
• Logical backup means backing up the individual database objects such as tables, schemas, views, indexes using the utility called EXPORT, provided by the Oracle. 
• A logical backup can be used to recover the contents of the database to the last backup.

Physical Backup

• Physical backups are backups of the physical files: such as datafiles, control files, and archived redo logs.
• Redo logs file contains all your transaction in binary format. 
• The following SQL query is used to view redo log files:

           SELECT * FROM V$LOG;

• This type of backup is often used to recover the database to the point of failure.

• Physical backup has two types:
• Online Backup and 
• Offline backup

• Online Backup (Consistent backup OR Hot backup)
• Pros: Pointing time recovery and no database shutdown
• Cons: Additional IO resources needed

• Offline Backup (Inconsistent backup OR Cold backup)
• Pros: Consistent and easy to manage
• Cons: No pointing time recovery and unavailability to end users