单项选择题
A.The backup is similar to image copy.
B.The backup contains all used data blocks.
C.The backup contains only unused data blocks.
D.The backup contains all data blocks changed since the last incremental level 1 backup.
单项选择题 You want to monitor and control the resource usage by sessions. You want to be warned automatically when more than 100 sessions are opened with your database. What action would you take to achieve this？（）
单项选择题 Theapplicationworkloadonyourdatabaseissamebetween10a.m.and11a.m.onweekdays.Suddenlyyouobservepoorperformancebetween10a.m.and11a.m.inthemiddleoftheweek.Howwouldyouidentifythechangesinconfigurationsettings，workloadprofile，andstatisticstodiagnosethepossiblecausesoftheperformancedegradation？（）
单项选择题 Your database is functional with peak load for one hour. You want to preserve the performance statistics collected during this period so that they can be used for comparison while analyzing the performance of the database in the future. What action would you take to achieve this task？（）