Which four are true about the Automatic Workload Repository (AWR)?
A)AWR data can be retained for a month.
B)It includes statistics on the number of columns in each view.
C)Automatic AWR snapshots can be written once per hour.
D)It includes statistics on the number of columns in each table.
E)Automatic AWR snapshots can be written once every 6 hours
F)AWR data can be retained for 3 months.
Answer: ACEF
赵：B、D 中的 statistics 说的是优化器收集统计信息功能，和 AWR 不是一个事。
