单项选择题 An index called ORD_CUSTNAME_IX has been created on the CUSTNAME column in the ORDERS table using the following command：   SQL>CREATE INDEX ord_custname_ix ON orders（custname）；   The ORDERS table is frequently queried using the CUSTNAME column in the WHERE clause. You want to check the impact on the performance of the queries if the index is not available. You do not want the index to be dropped or rebuilt to perform this test.  Which is the most efficient method of performing this task？（）

单项选择题 A PL/SQL procedure queries only those columns of a redefined table that were unchanged by the online table redefinition.  What happens to the PL/SQL procedure after the online table redefinition？（）

单项选择题 You create a new Automatic Database Diagnostic Monitor （ADDM） task：  instance_analysis_mode_task. To view the ADDM report， you use the following command：   SQL> SELECT dbms_addm.get_report（’my_instance_analysis_mode_task’） FROM dual；   You want to suppress ADDM output relating to Segment Advisor actions on user SCOTT’s segments.  What would you do to achieve this？（）