The EMP table exists in your schema. You want to execute the following query:
SELECT ename, sal
FROM emp
AS OF TIMESTAMP (SYSTIMESTAMP - INTERVAL '6' MINUTE)
WHERE ename = 'ALLEN';
What are the minimum requirements for the statement to execute successfully? (Choose all that apply)
A.ARCHIVELOG mode must be enabled
B.Row Movement must be enabled for the table
C.FLASHBACK must be set to ON for the database
D.The UNDO_MANAGEMENT parameter must be set to AUTO
E.The UNDO_RETENTION parameter must be set appropriately
此题考查闪回查询，因为闪回查询是基于 undo 数据的，所以只要保证闪回查询的那个时间点有 undo 数据就能够查询成功
使用闪回技术必须使用自动 undo 段管理的 undo 表空间，并且 UNDO_RETENTION 要设置一个合适的值。
A 错误，闪回技术和归档无关
B 错误，闪回表才需要开启行迁移，闪回查询并不需要
C 错误 flashback on 是开启闪回数据库，是基于闪回日志的。