Which three are true about thresholds, metrics, and server-generated alerts? (Choose three.)
A.All metrics are instance related. B.Cleared stateful alerts are displayed by querying DBA_ALERT_HISTORY. C.A space usage management alert is automatically cleared after the underlying problem is resolved. D.They are generated by SMON when a tablespace is 97% full. E.Metrics are statistical counts for a specific unit. F.STATISTICS_LEVEL must be set to ALL to generate alerts.正确答案BCE
