You want to take a complete database backup using RMAN. The backup should consist onlythe used blocks from your database. Which two statements are true about this backup operation？（） 

• A、 Backup compression should be enabled
• B、 Parallelism for the channel should be set to 2
• C、 All the files must be backed up as backup sets
• D、 The backup may be stored either on disk or on media with media manager