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. 
Answer: B   

A undo tablespace与备份无关
C 不对，当没有剩余空间时，commit超过15分钟的数据就会被覆盖掉
D flash recovery area 保存的是数据库快照 与 undo是不同的数据，undo不会进入 flash recovery are