32. Your database instance is running with full workload after database creation. You have decided to use
a fixed-size undo tablespace. You want to use the Undo Advisor to estimate the capacity of the undo
tablespace.
Which two factors must you consider before using the Undo Advisor to estimate the capacity of the undo
tablespace? (Choose two.)
A.the retention period to support flashback
B.the expected length of the longest-running query
C.the number of undo tablespaces in the database
D.the size of the Flash Recovery Area for the database instance
Answer: AB
答案解析：此题考的是，在固定大小的undo表空间，使用undo advisor来估算指定的还原保留时间所需要的还原表空间大小。
参考：http://blog.csdn.net/rlhua/article/details/12259555
还原指导。通过它可估计满足指定的还原保留时间所需要的还原表空间大小。
该指导的分析区域会显示支持保留时间所需的表空间大小。可以通过单击图上的某个点来查看支持选定期间所需要的表空间大小。
通过下图看出，undo advisor要考虑的两个因素是持续时间最长的查询和指定闪回持续更长时间。
