You have many users complaining about slow inserts into a large table. While investigating the reason， you find that the number of indexes on the table is high. You want to find out which indexes are not being used. 
Which method would you follow to achieve this？（）

多项选择题Users in your production database complain that they are getting the following error message while trying to insert rows into the ORDERS table：  ERROR at line 1：  ORA­01654： unable to extend index USERS.ORDERS_IND by 8 in tablespace INDEXES  While investigating， you find that the INDEXES tablespace has run out of space and there is no more free space on the disk where the data files are available.  Which two actions could you perform to overcome this error without affecting the queries that are currently being executed？（）

A.drop and re­create the index
B.coalesce the ORDERS_IND index
C.coalesce the INDEXES tablespace
D.drop and re­create the ORDERS table
E.rebuild the index online and move it to another tablespace

单项选择题In one of your online transaction processing （OLTP） applications， most users frequently modify the values， including the key values， of the application tables. Some users generate application reports by using multiple application tables.  What is the best table structure that you can use to gain optimal performance？（）

A.heap table
B.object table
C.external table
D.clustered table
E.global temporary table
F.index­organized table （IOT）

单项选择题In your test database， you have created the ORDERS table as an index­organized table （IOT）. To facilitate faster querying， you have created a mapping table and a bitmap index on the ORDER_FILLED column. You observe that the query performance degrades when users perform a large volume of transactions.  While investigating the reason， you find that the mapping table segment is fragmented， leading to poor performance. Which option would you use to defragment the mapping table without affecting the original table data？（）

A.export and import the mapping table
B.drop and re­create the mapping table
C.truncate the mapping table and reinsert the values
D.use the ALTER TABLE .. REBUILD command to defragment the mapping table

单项选择题You are designing an application for a telecom company and you have been asked to design a database table to facilitate monthly bill generation. The bill would include details of customer calls， listed in chronological order.  Which method would you follow to achieve this objective without increasing the overhead of sorting the rows？（）

A.create a hash cluster to store the data
B.create an index cluster to store the data
C.create a partitioned table to store the data
D.create a sorted hash cluster to store the data
E.create a heap table with rowid to store the data

单项选择题Inyourdatawarehousingapplication，yougeneratereportsfrequently.Thedataisstaticinthetablesbeingusedtogeneratereports.Youarecurrentlyusingjoins，resultinginalargeperformanceoverhead.Whatkindofdatabasestructurewouldyouusetoreducetheresponsetimeofthequery？（）

A.hash clusters
B.index clusters
C.partitioned tables
D.index­organized table （IOT）