6.1. An Overview of Flashback Technologies

Flashback Technologies consist of the Flashback Drop, Flashback Versions Query, Flashback Transaction Query, Flashback Table, and the supporting Recycle Bin. The Flashback Query, first made available in Oracle 9i, and the rest of the Flashback Technologies that are new to Oracle 10g all rely on the undo data to rebuild dropped objects. Undo data are the records of the changes of each update to an Oracle database and the values that were overwritten by those updates. In addition, the Flashback Technologies are enabled by default.

All of the Flashback Technologies are designed to recover from user error or logical corruption:

• The Flashback Table is designed to recover a table in situations such as when you update a table with the incorrect WHERE clause. This makes significant changes to the table that would require you to recover the whole table.

• The Flashback Versions Query is designed to see individual changes in the rows from query so that you can recover an individual row or column within the row.

• The Flashback Drop is designed so that users can undrop a table that was dropped by mistake.

• The Flashback Transaction Query is designed to perform diagnostics on the changes that occur in a table or query.

All of these technologies can be used together to fix almost any user error or logical corruption that occurs in a database.