OCP题库笔记1z0-052

OCP题库笔记1z0-052

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import
import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ADDM
ADDM runs after each AWR snapshot is collected automatically by MMON.
The results of the ADDM analysis are stored in th AWR.

6 关于Checkpoint
It 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.