CHAPTER 27Using Flashback Queries
As part of its read consistency model, Oracle displays data that has been committed to the database. As of Oracle9i, you can query data as it existed prior to a transaction being committed. If you accidentally commit an errant update or delete, you can use this capability—called a flashback query—to see the data as it existed prior to the commit. You can use the results of the flashback query to restore the data.
To support flashback queries, your database should use system-managed undo, a feature introduced in Oracle9i to automate management of rollback segments; see your DBA to determine if this feature is enabled in your environment. The DBA must create an undo tablespace, enable Automatic Undo Management, ...
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