You set the recovery window to seven days and the backup optimization to ON using the CONFIGURE
command of Recovery Manager (RMAN). The most recent backup of the TOOLS tablespace to disk was
taken on January 3. The TOOLS tablespace is read-only.
On February 21, when you execute a command to back up all the tablespaces to disk, you find that RMAN
backs up the TOOLS tablespace also, even though the contents of the tablespace have not changed after
the backup on January 3.
Because there are no changes made to the TOOLS tablespace, you decide that the tablespace should not
be backed up by RMAN. What can you do to skip backing up the TOOLS tablespace without changing the
current backup optimization setting?
A. configure a default device for RMAN backups
B. temporarily disable the retention policy for RMAN backups
C. configure automatic channel allocation for RMAN backups
D. use the CONFIGURE command to reconfigure the recovery window to 60 days
我个人做了个实验，在一个备份保留时期内，只读表空间是可以重复备份，只有将保留设为NONE，后只读表空间就不会再备份了。
所以正确答案应是：B
