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Wednesday, May 14, 2008

Oracle Flashback Technology

Oracle Flashback Technology

Flashback technology is reduce recovery time from minute to second.
Human error like by mistake update wrong table, drop table … etc.
To recover this error we have to perform database recovery but through flashback technology we can also correct this type of errors.
We can use flashback features to view past states of data and rewind parts or your entire database. In general, flashback features are more efficient and less disruptive than media recovery in most situations in which they apply.

Logical Flashback Features

Most of the flashback features of Oracle operate at the logical level, enabling you to view and manipulate database objects. The logical-level flashback features of Oracle do not depend on RMAN and are available whether or not RMAN is part of your backup strategy. With the exception of Flashback Drop, the logical flashback features rely on undo data, which are records of the effects of each database update and the values overwritten in the update.

Oracle Flashback Query
Flashback Query means we can see past data or query according specified time.

Oracle Flashback Version Query
Flashback Version Query means it is same like above but with this we can see all versions of all rows according specified period of time.

Oracle Flashback Transaction Query
Flashback Transaction Query queries the static data dictionary view FLASHBACK_TRANSACTION_QUERY. Use Flashback Transaction Query to obtain transaction information, including SQL code that you can use to undo each change that the transaction made.

Oracle Flashback Transaction

The DBMS_FLASHBACK.TRANSACTION_BACKOUT procedure ("TRANSACTION_BACKOUT") rolls back a transaction and its dependent transactions while the database remains online. This recovery operation uses undo data to create and execute the compensating transactions that return the affected data to its original state.

Oracle Flashback Table
Flashback Table uses information in the undo tablespace rather than restored backups to retrieve the table. When a Flashback Table operation occurs, rows are deleted and reinserted. The rest of your database remains available while the flashback of the table is being performed.

Oracle Flashback Drop
Flashback Drop reverses the effects of a DROP TABLE operation. Flashback Drop is faster than other recovery mechanisms that can be used in this situation, such as point-in-time recovery, and does not lead to downtime or loss of recent transactions

Oracle Flashback Database
The return of the whole database to a prior consistent SCN by means of the FLASHBACK DATABASE command in RMAN or SQL. A database flashback is different from traditional media recovery because it does not involve the restore of physical files, instead restoring your current datafiles to past states using saved images of changed data blocks. This feature uses
flashback logs and archived redo logs.

Read more about Oracle Flashback Technology

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