JAVA J2EE 4 U

SELECT 

    db_name,

    ROUND(AVG((completion_time - start_time) * 1440), 2) AS avg_full_backup_duration_mins

FROM 

    rc_backup_set

WHERE 

    backup_type = 'D'  -- 'D' = Datafile full backup

    AND status = 'A'   -- 'A' = Available (successful)

    AND start_time IS NOT NULL

    AND completion_time IS NOT NULL

    AND start_time >= SYSDATE - 30

GROUP BY 

    db_name;