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
答案解析：
参考：快速增量备份：http://blog.csdn.net/rlhua/article/details/12321679
通过启用块更改跟踪，可执行快速增量备份。块更改跟踪会将有更改的每个块的物理地址写入到一个文件中。需要执行增量备份时，RMAN 可查看块更改跟踪文件，并只备份该文件所引用的块，而无需通过扫描每个块来确定该块自上次备份以来是否发生过更改。
这会加快增量备份的速度。
只有同级之间的增量累积备份才有完全不一样更改过的块。故选C。