多项选择题

A.A backup of the target database when it is mounted
B.A backup of online redo log files when the database is open
C.A backup of only used data blocks in the file beingbeingbackup up
D.A backup of online, read/write data files when the database is open
E.A backup of only those data blocks that have changed since a previous backup
F.A backup of online, read/write data files when the database is in the NOMOUNT state.