Oracle Database has a group of features, known collectively as flashback, that provide ways to view past states of database objects, or to return database objects to a previous state, without using traditional point-in-time recovery.

• Flashback features of the database can be used to:
• Perform queries that return past data.
• Perform queries that return metadata showing a detailed history of changes to the database.
• Recover tables or individual rows to a previous point in time.

Flashback features use the Automatic Undo Management system to obtain metadata and historical data for transactions. They rely on undo data: records of the effects of individual transactions. Undo data is persistent and survives a database malfunction or shutdown. Using flashback features, you employ undo data to query past data or recover from logical corruptions. Besides your use of it in flashback operations, undo data is used by Oracle Database to do the following:

• rollback active transactions
• recover terminated transactions using database or process recovery
• provide read consistency for SQL queries

Quelle: Using Flashback Features, Oracle® Database Application Developer's Guide - Fundamentals 10g Release 1 (10.1)