Oracle: flashback usage

-- To save the flashback information for the last 30 minutes:
ALTER SYSTEM SET UNDO_RETENTION = 1800;

--
SELECT * FROM some_table AS OF TIMESTAMP ('2008-10-08 06:31:58', 'YYYY-MM-DD HH24:MI:SSS');

SELECT * FROM some_table AS OF SCN 12345678;

-- dbms_flashback could be also used
EXECUTE dbms_flashback.enable_at_time ('18-JAN-08 11:00:00');