1.One of your databases has archive logging enabled and RMAN backups are taken at regular intervals.

　　The data file for the users tablespace is corrupt.

　　Which command must you execute before starting the recovery of this tablespace ?

　　A) SWITCH DATAFILE ALL;

　　B) ALTER TABLESPACE users OFFLINE TEMPORARY;

　　C) STARTUP FORCE

　　D) ALTER TABLESPACE users OFFLINE IMMEDIATE;

　　E) ALTER TABLESPACE users OFFLINE NORMAL;

　　Answer:D

　　(解析：由于数据文件损坏，所以表空间无法正常 offline，会报错，只能用 immediate 选项。

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