（27）Which two statements are true regarding transactions in an Oracle database? (Choose two.)

A.Multiple transactions can use the same undo segment.

B.A transaction is assigned an undo segment when it is started.

C.More than one transaction cannot share the same extent in the undo tablespace.

D.The transactions use system undo segment to store undo data if all the segments in the undo tablespace are used.

答案：（A、B）

解析：

C（X）. 多个事务可以共享一个段，而段是由extent组成的，所以多个事务可以共享多个extent

D（X）. 应该是循环使用

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Oracle 11G OCP 1Z0-052 27