单项选择题 YouworkasadatabaseadministratorforSupportcenter.cn.Youenabledtracingwhilecreatingalistenertoyourdatabase.Whatadditionalinformationisavailabletoyouwhenyouenabletracing？（）

单项选择题 YouworkasadatabaseadministratorforSupportcenter.cn.YouwanttobenotifiedwhenthenumberofdiskI/Oincreasesby10%ofwhatitwasyesterday.Youcreateabaselinemetricforyesterday’sdiskI/Operformance.Howdoyouusethebaselinemetricstoachieveyourobjective？（）

单项选择题 You work as a database administrator for Supportcenter.cn. Users complain that their query is taking a long time to complete. You suspect the database buffer cache size to be the reason， and you define an alert to be generated when the buffer cache hit metric goes below 85%. When you observe the dynamic performance views， you find that the buffer cache hit ratio is 81% but no alerts are being generated.  What could be the reason for this problem？（）