Oracle Flashback in 10g

Using a new type of recovery log (called a flashback log ), the Flashback feature allows you to perform queries that return past data, or the history of changes on a particular table, to undo undesirable changes to a particular table. With flashback feature enabled is possible also to recover a table or the entire database to a previous point in time.

In this picture we can see that the Oracle Flashback is not enabled. Oracle Flashback is not enabled by default.

DB_RECOVERY_FILE_DEST

Setting the location of the flashback
recovery area.

Specifying this parameter without also specifying the DB_RECOVERY_FILE_DEST_SIZE initialization parameter is not allowed.

Syntax:

DB_RECOVERY_FILE_DEST = directory | disk group

Default value: There is no default value.

Modifiable ALTER SYSTEM ... SID='*'

For Real Application Clusters uou must set this parameter for every instance, and multiple instances must have the same value.

DB_RECOVERY_FILE_DEST_SIZE

Setting the size of the flashback
recovery area (by default in bytes)

Syntax:

DB_RECOVERY_FILE_DEST_SIZE = integer [K | M | G]

Default value: There is no default value.

Modifiable ALTER SYSTEM ... SID='*'

For Real Application Clusters you must set this parameter for every instance, and multiple instances must have the same value.

DB_FLASHBACK_RETENTION_TARGET

Setting the retention time for flashback files (in minutes)

( OPTIONAL )

Syntax:

DB_FLASHBACK_RETENTION_TARGET =integer

Default value: 1440 (minutes)

Modifiable ALTER SYSTEM

Range of values 0 to 4294967295

(0 to max value represented by 32 bits)

In my care I use pfile initialization file. I add the following parameters to the pfile:

*.db_recovery_file_dest='C:/flash_recovery_area'
*.db_recovery_file_dest_size=2147483648

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.

Total System Global Area 167772160 bytes
Fixed Size 1247900 bytes
Variable Size 62915940 bytes
Database Buffers 100663296 bytes
Redo Buffers 2945024 bytes
Database mounted.
SQL> alter database archivelog;

Database altered.

SQL> alter database flashback on;

Database altered.

SQL> alter database open;

Database altered.

SQL> SELECT FLASHBACK_ON, LOG_MODE FROM GV$DATABASE;

FLASHBACK_ON     LOG_MODE
---------------------          ------------
YES                              ARCHIVELOG

4. Which are the features related to the Oracle Flashback ?

The Recycle Bin is a virtual container where all dropped objects reside. Underneath the covers, the objects are occupying the same space as when they were created. If table EMP was created in the USERS tablespace, the dropped table EMP remains in the USERS tablespace. Dropped tables and any associated objects such as indexes, constraints, nested tables, and other dependant objects are not moved, they are simply renamed with a prefix of BIN$$. You can continue to access the data in a dropped table or even use Flashback Query against it. Each user has the same rights and privileges on Recycle Bin objects before they were dropped. You can view your dropped tables by querying the new RECYCLEBIN view. Objects in the Recycle Bin will remain in the database until the owner of the dropped objects decides to permanently remove them using the new PURGE command. The Recycle Bin objects are counted against a user's quota. But Flashback Drop is a non-intrusive feature. Objects in the Recycle Bin will be automatically purged by the space reclamation process if