-- 설정된 제한 시간 확인
SELECT * FROM V$PARAMETER WHERE NAME = 'db_flashback_retention_target';

-- 30분전
SELECT * FROM ESAUSER AS OF TIMESTAMP SYSDATE - 30 / (24 * 60);

-- 특정시점
SELECT * FROM ESAUSER AS OF TIMESTAMP TO_DATE('20151013010000', 'YYYYMMDDHH24MISS');