Which two operations require undo data？（）

A.You have to shut down the database to perform the backups.
B.Archiving information is written to the data files and redo log files.
C.You can perform complete database backups without closing the database.
D.Online redo log files have to be multiplexed before putting the database in ARCHIVELOG mode.
E.All the previous database backups become invalid after you configure the database to ARCHIVELOG mode.

A.current redo log and inactive redo log
B.checkpoint position to end of redo log
C.beginning of redo log to end of redo log
D.all redo logs before the point of last commit
E.beginning of redo log to checkpoint position

A.The user must be granted the database administrator （DBA） privilege.
B.The user must be listed in the password file for the authentication.
C.No special setup is needed for the user to connect as SYSDBA in iSQL*Plus.
D.Set up a user in the Oracle Application Server Containers for J2EE （OC4J） user manager，and grant the webDba role to the user.