Which two are true about RMAN duplexed backup sets? (Choose two.)
A.A duplexed backup set uses the same number of SBT channels as a non-duplexed backup set for the same number of files. B.A non-duplexed backup set written to disk can be duplexed to disk by backing up the backup set that is already on disk. C.A non-duplexed backup set written to SBT can be duplexed to tape by backing up the backup set that is already on tape. D.A non-duplexed backup set written to disk can be duplexed to tape by backing up the backup set that is already on disk. E.A non-duplexed backup set written to SBT can be duplexed to disk by backing up the backup set that is already on tape. F.A duplexed backup set always uses twice as many SBT channels as a non-duplexed backup set for the same number of files.正确答案BD
