OCP题库笔记1z0-052

来源:互联网 时间:1970-01-01

1 关于undo

数据库可以有一个以上的undo表空间;undo段可以自动增长,按需shrink
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。
3 关于无效索引会被优化器忽略;只能通过rebuild生效。
4 关于监听多个监听能运行在一个主机上;多个数据库能注册在一个监听上。
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.


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