You have enabled backup optimization in RMAN. You issue the following RMAN command to
configure a redundancy-based retention policy:
CONFIGURE RETENTION POLICY TO REDUNDANCY 3;
Which statement is true?
A. The command fails because you cannot configure a redundancy-based retention policy when backup optimization is enabled
B. Backup optimization is performed, but RMAN considers the redundancy-based retention policy when it determines which datafiles should be backed up
C. Backup optimization is permanently disabled
D. Backup optimization is temporarily disabled because a redundancy-based retention policy is specified
此题考点是备份优化，备份优化会遵守原来的备份设置。只是在此基础上对一些不必要的文件进行忽略，加快备份速度。
备份优化会考虑备份策略，如果不满足备份策略，仍然会对所有文件进行备份，忽略备份优化。如果在满足备份策略的情况下，会跳过离线的数据文件。
注：你可以使用 force 选项来覆盖备份优化配置。使用 BACK .... DELETE INPUT 会删除指定的归档日志文件，不管这些文件是否被备份优化跳过