ocp 053

648.Note the following statements that use flashback technology:

1. FLASHBACK TABLE <table> TO SCN <scn>;

2. SELECT * FROM <table> AS OF SCN 123456;

3. FLASHBACK TABLE <table> TO BEFORE DROP;

4. FLASHBACK DATABASE TO TIMESTAMP <timestamp>;

5. SELECT * FROM <table> VERSIONS AS OF SCN 123456 AND 123999;

Which of these statements will be dependent on the availability of relevant undo data in the undo

segment?

A. 1, 2, and 5

B. 1, 3, and 4

C. 2, 3, 4, and 5

D. 1, 2, 3, 4, and 5

Answer: A

 答案解析：

参考：闪回数据库：http://blog.csdn.net/rlhua/article/details/12421005

闪回表和闪回版本查询：http://blog.csdn.net/rlhua/article/details/12404577

闪回删除：http://blog.csdn.net/rlhua/article/details/12407737

1.闪回表原理是还原数据。

2.闪回查询是还原数据。

3.闪回删除是回收站原理。

4.闪回数据库是基于闪回日志。

5.闪回版本查询是基于还原数据。

所以基于还原数据的是125.