OCP題庫筆記1z0-052

1 關於undo
資料庫可以有一個以上的undo資料表空間；
undo段可以自動成長，按需shrink

2 關於Oracle Data Dump export和import
import操作同時可以更改表名；
可以在export操作期間重寫一個存在的dumpfile。

3 關於無效索引
會被最佳化器忽略；
只能通過rebuild生效。

4 關於監聽
多個監聽能運行在一個主機上；
多個資料庫能註冊在一個監聽上。

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

6 關於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關於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 關於會話
Multiple transactions can use the same undo segment.
A transaction is assigned an undo segment when it is started.