OCP 1Z0 053 78

78.You enable block change tracking. You issue the following command: 
BACKUP INCREMENTAL LEVEL 0 DATABASE; 
The next day, you issue the following command: 
BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE; 
Which statement about the use of the change tracking file is true? 
A. RMAN reads the block change tracking file only when it performs the incremental level 0 backup. 
B. RMAN reads the block change tracking file when it performs both incremental backups. 
C. RMAN reads the block change tracking file only when it performs the incremental level 1 backup. 
D. RMAN does not read the block change tracking file when it performs either incremental backup. 
Answer: C 

0是全备，1是在上一个0或上一个1级上的增备

http://docs.oracle.com/cd/E11882_01/backup.112/e10643/rcmsynta007.htm#RCMRF90009

Incremental Backups

An INCREMENTAL backup at level 0 backs up all data blocks in data files being backed up. An incremental backup at level 0 is identical in content to a FULLbackup, but unlike a full backup the level 0 backup is a part of the incremental backup strategy.

A level 1 backup copies only changed blocks. A level 1 incremental backup is either differential or CUMULATIVE. If cumulative, RMAN backs up all blocks changed since the most recent level 0 backup. If differential, RMAN backs up blocks updated since the most recent level 0 or level 1 incremental backup. You can apply a level 1 backup of a standby database to a level 0 backup of a primary database, and also apply a level 1 backup of a primary database to a level 0 backup of a standby database.

Incremental backups at level 0 can be either backup sets or image copies, but incremental backups at level 1 can only be backup sets.