052-003題解析

3.

While observing the index statistics, you find that an index is highly fragmented, thereby resulting in poor database performance. Which option would you use to reduce fragmentation without affecting the users who are currently using the index?

A.Validate the index structure using the ANALYZE...INDEX command.

B.Rebuild the index using the ALTER INDEX..REBUILD ONLINE command.

C.Change the block space utilization parameters using the ALTER INDEX command.

D.Deallocate the unused space in the index using the ALTER INDEX..DEALLOCATE UNUSED command.

Answer: B

答案解析：

透過重建不可用索引來重算指標，可使不可用索引變為有效。重建不可用索引會在新位置重新建立索引，然後會刪除不可用索引。如使用一下語句來重建索引

ALTER INDEX HR.emp_empid_pk REBUILD ONLINE;

使用REBUILD ONLINE子句，使用者可以在重建時繼續更新索引表。