You are using the control file to maintain information about the database backups that are being performed by Recovery Manager (RMAN). Identify two scenarios is which you must have a recovery catalog.（）
- A To store the backup information of multiple database
- B To restrict the amount of space that is used by the backups
- C To maintain a backup for a certain time is set by the CONTROL_FILE_RECORD_KEEP_TIME parameter.
- D To list the data files that were in a target database at a given time by using the AT option of REPORT SCHEMA command.