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Flashback Technology : Overview

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Flashback Technology : Overview

 

Flashback Query : introduced in Oracle 9i. Flashback Query allows to query the databases as it was in the recent past. Flashback Query depend on undo data and undo retention.

 

Flashback Table to a scn or to a timestamp : to recover a table or some tables to a previous point in time. Flashback Table depend on undo data and undo retention and requires that table row movement is enabled prior to the flashback flashback operation. Flashback Table is rather meant for recovery off logical errors which occured in the recent past.

 

Flashback Table to before drop : to recover a table dropped by accident.  Flashback Table to before drop depend on the recycle bin which is available by default ( parameter recyclebin )

 

Flashback Versions Query : allows to query multiple states of a record ( row ), multiple versions can be queried between a startscn and endscn.

 

Flashback Transaction Query : allows to query the transaction which changed the state of the record ( row ) Flasback Transaction Query can be used to retrieve the undo SQL. This undo SQL can then be used to revert the row change. Flashback Transaction Query is related to Log Miner. Minimal supplemental redo logging must be enabled.

 

Flashback Transaction Backout : to backout transactions ( and dependent transactions ) Flashback Transaction Backout is related to Log miner.Minimal supplemental redo logging and supplemental logging for the primary key must be enabled and the database must operate in archivelog mode.

 

Flashback Data Archive : when a row is changed the before image - previous state of the row - is kept in an archive table.

 

Flashback Database : can be used to rewind temporary are permanently back. Flashback database is rather meant for point in time recovery to recover from logical errors.