增量备份分为差异备份（differential incremental backup）和累积备份（cumulative incremental backup），这是两种执行增量备份操作的不同方法。

80. You perform differential incremental level 1 backups of your database on each working day and level 0

backup on Sundays, to tape. 

Which two statements are true about differential incremental backups? (Choose two.)

A.The backup performed on Sundays contains all the blocks that have ever been used in the database.

B.The backup performed on Sundays contains all the blocks that have changed since the last level 1

backup.

C.The backup performed on each working day contains all the blocks that have changed since the last

level 0 backup.

D.The backup performed on Monday contains all the blocks that have changed since the level 0 backup,

and every other working day contains all the blocks that have changed since the level 1 backup.

Answer: AD  

题目备份策略如下：

执行增量备份操作时，首先需要的是增量基本备份(incremental base backup),即level 0，今后所有的增量备份都是基于这个基本备份的。

每次执行数据库的备份操作时，都可以通过backup命令incremental参数来为备份派一个增量级别标识符。

基本备份的增量级别为0，并且必须有基本备份才能够执行其它类型的增量备份操作。

如果没有生成基本备份就尝试执行增量备份操作（这个增量备份操作使用0以外的备份级别），RMAN就自动执行基本备份操作。

下面是一个执行基本增量备份操作的命令：

1、首先使用rman连接目标库。 rman target /

2、执行0级增量备份。                   backup incremental level 0 database

3、执行1级增量备份。          backup incremental level 1 database;

82、You are managing an Oracle Database 11g database with the following backup strategy:

1) On Sunday, an incremental level 0 tape backup is performed.

2) Monday through Saturday, a cumulative incremental level 1 tape backup is performed.

Which two statements are true regarding the backups performed? (Choose two.)

A.The backup performed in step 1 backs up all blocks that have ever been in use in the database.

B.The backup performed in step 2 copies all the blocks changed since the most recent level 0 backup. 

C.The backup performed in step 1 backs up all the blocks changed since the most recent level 1 backup.

D.The backup performed in step 2 backs up all blocks that have changed since the most recent

incremental backup at level 1.

Answer: AB  

备份策略如下：

此题考的是增量累积备份