Which three are true about the Automatic Workload Repository (AWR)?
A)AWR data is stored in the SYSTEM tablespace.
B)By default, AWR snapshots are taken every 60 minutes.
C)It is the foundation for the self-managing infrastructure.
D)The taking of AWR snapshots cannot be disabled.
E)Its collection level is determined by the value of the STATISTICS_LEVEL database parameter.
F)It is used by the Optimizer to determine optimal execution plans.
Answer: BCE
赵：F 错，优化器使用的是统计信息，不是 AWR。
