SELECT table_name, total_phys_io
  FROM (  SELECT owner || '.' || object_name AS table_name,
                 SUM (VALUE) AS total_phys_io
            FROM v$segment_statistics
           WHERE owner != 'SYS' AND object_type = 'TABLE'
                 AND statistic_name IN
                        ('physical reads',
                         'physical reads direct',
                         'physical writes',
                         'physical writes direct')
        GROUP BY owner || '.' || object_name
        ORDER BY total_phys_io DESC)
 WHERE ROWNUM <= 10;