Oracle 11G OCP 1Z0-052 29

（29）Your database instance is configured with automatic undo management and the UNDO_RETENTION parameter is set to 900 seconds.

You executed the following command to enable retention guarantee: SQL> ALTER TABLESPACE undotbs1 RETENTION GUARANTEE;

What effect would this command have on the database?

A.The extents in the undo tablespace retain data until the next full database backup.

B.The extents containing committed undo in the undo tablespace are not overwritten for at least 15 minutes.

C.The extents containing committed data in the undo tablespace are not overwritten until the instance is shut down.

D.The extents containing committed undo in the undo tablespace are transferred to Flash Recovery Area before being overwritten.

答案：（B）

解析：

A（X）. 設定undo保留期與備份沒有任何關係

C（X）. 被提交的事務的undo資料，是有可能被覆蓋的（這取決於資料檔案是否是自動增長，及是否設定了保留期保證）

D（X）. 不存在

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