Saber os usuários do Banco de dados Oracle

Conectado com o usuário system:

select username
from dba_users
where username
not in('QS_CB','PERFSTAT','QS_ADM',
'PM','SH','HR','OE',
'ODM_MTR','WKPROXY','ANONYMOUS',
'OWNER','SYS','SYSTEM','SCOTT',
'SYSMAN','XDB','DBSNMP','EXFSYS',
'OLAPSYS','MDSYS','WMSYS','WKSYS',
'DMSYS','ODM','EXFSYS','CTXSYS','LBACSYS',
'ORDPLUGINS','SQLTXPLAIN','OUTLN',
'TSMSYS','XS$NULL','TOAD','STREAM',
'SPATIAL_CSW_ADMIN','SPATIAL_WFS_ADMIN',
'SI_INFORMTN_SCHEMA','QS','QS_CBADM',
'QS_CS','QS_ES','QS_OS','QS_WS','PA_AWR_USER',
'OWBSYS_AUDIT','OWBSYS','ORDSYS','ORDDATA',
'ORACLE_OCM','MGMT_VIEW','MDDATA',
'FLOWS_FILES','FLASHBACK','AWRUSER',
'APPQOSSYS','APEX_PUBLIC_USER',
'APEX_030200','FLOWS_020100');

Fonte: CertificaçãoBD