Flashback Operations

The flashback query feature was introduced in Oracle 9i. In Oracle Database 10g, this functionality has been expanded to include several powerful options, and for use with the entire database. All flashback features rely on the database undo information to re-create a state in the past. Flashback transaction query, flashback versions query, Flashback Table, and Flashback Database are the major flashback operations. A more detailed explanation of flashback operations is given in Chapter 17, "Effectively Using Flashback Technologies."

Flashback Database

Flashback Database is a new feature introduced in Oracle Database 10g. This feature helps the DBA to quickly revert an entire Oracle database to a former state at any past point in time. It is different from the traditional point-in-time recovery used from Oracle 7.x version until 9i.

You can use Flashback Database to back out of changes to the database that are caused by user errors and that have resulted in logical data corruptions. It is not useful for recovering the database in case of media (disk) failures.

The actual time needed to flashback a database to a point in the past is directly proportional to the number of changes made to the database during that duration and not dependent on the actual size of the database.

Using this fetaure is faster than point-in-time recovery using backups and redo log files. The database must be mounted in an exclusive state to perform the flashback operation. We will review this in detail in Chapter 17.