052-80

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.

　　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。
　　0 级增量备份会备份所有曾经在此数据库中使用的块。
　　从星期一到星期六的每一天，1 级增量备份备份最近 1 或 0 级增量备份以来所有更改过的块。周一备份周日 0 级备份以来变化的块，周二备份周一 1 级备份改变的块，等等。
　　第一个周日 0级备份(all the blocks)
　　　　　　　　　↓
　　周一 1级备份(基于0级备份后变更的blocks，周日备份后变更的块)
　　　　　　　　　↓
　　周二 1级备份(基于上次1级备份后变更的blocks，周一备份后变更的块)
　　　　　　　　　……
　　　　　　　　　↓
　　第二个周日 0级备份(all the blocks)