单项选择题
A.It terminates all user sessions.
B.It prevents users from logging in to the database remotely.
C.It halts the server until all user transactions are completed.
D.The server hangs， so users will receive an error asking them to login again.
E.Connected users would get an error with the message "End of communication channel".
单项选择题 You have a production instance running on your server. UNDO_RETENTION is not long enough to satisfy read-consistency requirements. How do you change the UNDO_RETENTION value？（）
多项选择题 Inwhichtwocaseswouldyouperformonlyconsistentbackup？（）
单项选择题 DuetomediafailureyoulostoneofthedatafilesbelongingtotheUSERStablespace，andthetablespaceisnotavailabletouse.Whichstatementregardingthestatusofthedatabaseistrue？（）