单项选择题
A.alter database controlfile autobacku on
B.alter system controlfile autobackup on
C.configure controlfile autobackup on
D.enable controlfile autobackup
单项选择题 Whichcommanddoyouusetocreatearecovery-catalogschema?（）
单项选择题 WhatcommandwouldyouusetosetapersistentsettinginRMANsothatbackupsareallwrittentoatapedevice?（）
单项选择题 Whatfeaturecomesintoplaytohelpensurethecompletionofthebackupshouldoneofthreebackupdevicesfailduringabackupthatisusingthreedifferentchannels?（）