OCP-1Z0-053-V12.02-143题

143.Which two are the prerequisites to enable Flashback Data Archive? (Choose two.)

A. Database must be running in archivelog mode.

B. Automatic undo management must be enabled.

C. Undo retention guarantee must be enabled.

D. The tablespace on which the Flashback Data Archive is created must be managed with Automatic

Segment Space Management (ASSM).

Answer: BD

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12221269

官方参考：http://docs.oracle.com/cd/E11882_01/appdev.112/e41502/adfns_flashback.htm#ADFNS01001

Oracle Flashback features use the Automatic Undo Management (AUM) system to obtain metadata and historical data for transactions. They rely on undo data, which are records of the effects of individual transactions. For example, if a user runs an UPDATE statement to change a salary from 1000 to 1100, then Oracle Database stores the value 1000 in the undo data.

Undo data is persistent and survives a database shutdown. By using flashback features, you can use undo data to query past data or recover from logical damage.