Restore user errors using the Flashback database feature in Oracle

ORACLE10G has a new feature flashback Database that, when you start it, periodically writes the changed chunks to the log file of the flashback log. Note that these logs are not written by the traditional log Writer (LGWR) procedure, but by a new process called recovery Writer.

$ ps -ef|grep rvwr|grep -v grep
oracle 27231　　 1　0 17:10:30 ?　　　　0:00 ora_rvwr_eygle

Note: Unlike regular redo logs, the flash logs do not require DBA creation or DBA maintenance, and they are automatically created by Oracle Managed Files (OMF) in the directory specified in the Flashback recovery area. Note that these files are not archived, so if there is a media failure in the directory, it is not possible to recover.

(1) First enable the Flash back database feature

SYS as SYSDBA on 2005-03-29 16:42:19 >startup mount;
ORACLE instance started.
Total System Global area 314572800 bytes
Fixed Size 1301704 bytes
Variable Size 261890872 bytes
Database buffers 50331648 bytes
Redo buffers 1048576 bytes
Database mounted.
SYS as SYSDBA on 29-mar-05 >alter database archivelog;
Database altered.
SYS as SYSDBA on 29-mar-05 >alter the database flashback on;
Database altered.
SYS as SYSDBA on 29-mar-05 >alter database open;
Database altered.
SYS as SYSDBA on 29-mar-05 >alter session set nls_date_format=
' Yyyy-mm-dd hh24:mi:ss ';
Session altered.
SYS as SYSDBA on 2005-03-29 17:01:42 >select OLDEST_FLASHBACK_SCN,
oldest_flashback_time 2 from V$flashback_database_log;
Oldest_flashback_scn oldest_flashback_ti
---------------------------------------
10642627 2005-03-29 1 7:01:02

(2) Flash back log

Note: Oracle will log logs in the Flash-back area.

$ pwd
/data5/flash_recovery_area/EYGLE/flashback
$ ls -l
total 32064
-rw-r-----　 1 oracle　 dba　　　8200192 Mar 29 16:49 o1_mf_14l5bclp_.flb
-rw-r-----　 1 oracle　 dba　　　8200192 Mar 29 17:31 o1_mf_14l6w5h4_.flb