Oracle Flashback technology provides several fast recovery options including Flashback Query, Flashback Version, Flashback Transaction, Flashback Table, and Flashback Drop. These features allow recovering data to a prior state by undoing changes or retrieving dropped objects without fully restoring backups. Flashback options can recover from corruptions, errors, disasters, and restore lost data through interfaces like easy-to-use Flashback commands.

1. Oracle
Flashback

2. • Flashback technology is a revolutionary advancing recovery
• Traditional recovery techniques are slow
– Entire database or file has to be restored, not just the incorrect
data
– Every change in the database log must be examined
• Flashback is fast
– Changes are indexed by row and by transaction
– Only the changed data is restored
• Flashback commands are easy
– No complex multi-step procedures
Flashback Technology
Benefits

3. When to Use Flashback
Technology
Flashback technology should be used when a logical corruption occurs in
the Oracle database,and you need to recover quickly and easily.

4. • Corruptions
• Human
Errors
●Deletions
●Truncatio
ns
●Drops
• Disasters
• Power Outage
• Hardware Failure
• Flashback Database brings the database to a prior point in time by undoing all
changes made since that time.
• Flashback Table recovers a table to a point in time in the past without
restoring a backup.
• Flashback Drop restores accidentally dropped tables.
Flashback Any
Error

5. Flashback
Database

6. • Flashback Query – allows a user to view previous versions of a table.
• Flashback Version – allows changes of individual rows to be tracked.
• Flashback Transaction – allows tracking of specific transaction
changes.
• Flashback Table – put the table back as it was, undoing corruption
• Flashback Drop – retrieve a dropped table from the recyclebin
Flashback Database
Feature

7. • SHUTDOWN IMMEDIATE
• STARTUP MOUNT
• ALTER DATABASE FLASHBACK ON
• Set the Flashback Database retention target:
– DB_FLASHBACK_RETENTION_TARGET
The default value for flashback retention time is 1400 minutes.
• ALTER DATABASE OPEN
• Select CURRENT_SCN, FLASHBACK_ON From V$DATABASE
To monitor Flashback Database use
sql> select * from v$flashback_database_stat
Configuring Flashback
Database
SQL> ALTER SYSTEM SET
DB_FLASHBACK_RETENTION_TARGET=2880
SCOPE=BOTH;

8. • Performing a FLASHBACK DATABASE recovery:
– SHUTDOWN IMMEDIATE
– STARTUP MOUNT
– FLASHBACK DATABASE to SCN <scn>
– ALTER DATABASE OPEN RESETLOGS
• FLASHBACK DATABASE recovery options:
– FLASHBACK DATABASE to TIMESTAMP <date>
– FLASHBACK DATABASE to BEFORE SCN <scn>
– FLASHBACK DATABASE to BEFORE TIMESTAMP
<date>

9. 1- Flashback
Query
sql> select current_scn from v$database
-----------2045116-----------
select * from thach_vekyou.bk_emp
----delete all row of bk_emp table-------
sql> delete from thach_vekyou.bk_emp
----get back all row which lost----------
sql> insert into thach_vekyou.bk_emp (select * from
thach_vekyou.bk_emp as
of scn 2045116)
• Allows Querying of data in the past
• CURRENT_SCN from V$DATABASE;

10. 2- Flashback Version
Query
●With the Flashback Query feature, you can perform queries on the
database as of a certain time or user-specified system change number
(SCN).
●The Flashback Versions Query feature allows you to use the VERSIONS
clause to retrieve all of the versions of the rows that exist between two
points in time, or two SCNs.

11. Flashback Version Query
Example

12. Flashback Transaction Query is a diagnostic tool you can use to view
changes made to the database at the transaction level.
3- Flashback Transaction
Query
SELECT operation, undo_sql, table_name
FROM FLASHBACK_TRANSACTION_QUERY;
●returns information about all
transactions
Exmapl
e
SELECT operation, undo_sql, table_name
FROM FLASHBACK_TRANSACTION_QUERY
WHERE xid = HEXTORAW('8C0024003A000000')
ORDER BY undo_change#;
●returns information about all transactions with
condition xid
SELECT operation, undo_sql, table_name
FROM FLASHBACK_TRANSACTION_QUERY
WHERE start_timestamp >= TO_TIMESTAMP ('2009-04-21 11:00:00',
'YYYY-MM-DD HH:MI:SS‘) AND commit_timestamp <= TO_TIMESTAMP
('2003-10-21 11:30:00','YYYY-MM-DD HH:MI:SS');
●returns information about transactions in
timestamp

13. Using Flashback Versions Query and Flashback Transaction
Query
• The view contains a column ‘XID’ which can be joined to the
‘VERSIONS_XID’ row returned by the ‘VERSIONS_BETWEEN’
clause.

14. 4- Flashback
Table
• Allows a table to be rolled back to a particular point in time
• The relevant information ‘ROW MOVEMENT’ must be enabled.
• When you use the Flashback Table feature to restore a table to a specific
point in time, all associated objects, such as, indexes, constraints, and
triggers will be restored.
• Flashback Table allows you to recover a table or tables to a specific point
in
time without restoring a backup.

15. 5- Flashback
Drop
• Acts as a ‘RECYCLEBIN’ allowing dropped tables to be retrieved
• Flashback Drop is a variation of Flashback table as it handles rolling
back a dropped table.
• Dropped tables are ‘RENAMED’ in the ‘RECYCLEBIN’ and can be retrieved
using the ‘FLASHBACK DROP’ command.
• Tables must be in Locally managed tablespaces
• Tables must not be in the SYSTEM tablespace
• The relevant information ‘ROW MOVEMENT’ must be enabled.

16. Examp
le

17. The End
Author : Thach
Vekyou
http://top10town.com