2 关于Oracle Data Dump export和importimport操作同时可以更改表名；可以在export操作期间重写一个存在的dumpfile。
5 关于ADDMADDM runs after each AWR snapshot is collected automatically by MMON.The results of the ADDM analysis are stored in th AWR.
6 关于CheckpointIt ensures that all committed data is written to the data files during normal shutdown.The frequent full checkpoint in a database can cause the overall degradation of the database performance.
7关于B-tree索引The leaf blocks in the index are doubly linked.The deletion of a row frin the table cause a logical deletion in index leaf block and the space becomes available for the nre leaf entry.
8 关于会话Multiple transactions can use the same undo segment.A transaction is assigned an undo segment when it is started.