Réponses:
Regardez la vue "dba_segments" (ou user_segments si vous n'avez pas les droits dba). La requête suivante devrait vous donner ce que vous recherchez:
select
owner as "Schema"
, segment_name as "Object Name"
, segment_type as "Object Type"
, round(bytes/1024/1024,2) as "Object Size (Mb)"
, tablespace_name as "Tablespace"
from dba_segments
order by owner;