sysseg.sql

rem    This script list all segments that reside in the SYSTEM tablespace other that those
rem    owned by SYS and SYSTEM. It is bad practice to store non-dictionary information in
rem    the SYSTEM tablespace.

spool sysseg.lis 

select segment_name from dba_segments
where owner not in ('SYS', 'SYSTEM')
and   tablespace_name='SYSTEM'
/

spool off