prompt
prompt Objects existing in the SYSTEM tablespace
prompt -----------------------------------------
pause

prompt Objects other than those owned by SYS or SYSTEM should exist in
prompt their own tablespace

col Owner format a17 heading 'Owner'
col ob_type format a4 heading 'Type'
col ob_name format a30 heading 'Object'
col size_m format 990.90 heading 'Size M'

break on owner nodup skip 1 on report
compute sum of size_m on owner report

select owner, decode(substr(segment_type,1,3), 'TAB', 'Tbl:',
'IND', 'Idx:',
substr(segment_type,1,3)||':') ob_type,
segment_name ob_name, bytes/(1024*1024) size_m
from dba_segments
where tablespace_name = 'SYSTEM'
and owner not in ('SYS', 'SYSTEM')
order by 1,3
/