FLASHBACK DATABASE

Assuming that you have prepared a flash recovery area for the database and enabled media recovery, enable database FLASHBACK mode and open the database with the following statements:
STARTUP MOUNT
ALTER DATABASE FLASHBACK ON;
ALTER DATABASE OPEN;


With your database open for at least a day, you can flash back the database one day with the following statements:
SHUTDOWN DATABASE
STARTUP MOUNT
FLASHBACK DATABASE TO TIMESTAMP SYSDATE-1;
ALTER DATABASE OPEN RESETLOGS;

OR

STARTUP FORCE MOUNT
FLASHBACK DATABASE TO TIMESTAMP TO_TIMESTAMP('24-11-2011 10:12:12','DD-MM-YYYY HH24:11:2011');
ALTER DATABASE OPEN RESETLOGS