SELECT 
    l.segment_name               AS object_name
   ,SUM(l.bytes) /1024/1024/1024 AS gbytes
FROM dba_segments L
WHERE l.owner = 'HR'
GROUP BY l.segment_name
ORDER BY gbytes DESC;

SELECT 
    o.owner, 
    l.oracle_username, 
    l.os_user_name, 
    l.session_id||','||v.serial# AS sid_serial, 
    l.oracle_username AS ora_user, 
    o.object_name, 
    o.object_type, 
    l.oracle_username, 
    DECODE(l.locked_mode, 
            0, 'None', 
            1, 'Null', 
            2, 'Row-S (SS)', 
            3, 'Row-X (SX)', 
            4, 'Share', 
            5, 'S/Row-X (SSX)', 
            6, 'Exclusive', 
            TO_CHAR(l.locked_mode) 
          ) AS lock_mode, 
    o.status,
    v.service_name,
    TO_CHAR(o.last_ddl_time,'DD.MM.YY HH24:MI') AS last_ddl 
    o.*,
    l.*,
    v.*
FROM 
    dba_objects o, 
    gv$locked_object l, 
    v$session v 
WHERE 
    o.object_id = l.object_id 
    AND l.SESSION_ID = v.sid 
ORDER BY 
    l.oracle_username,
    l.os_user_name;