SQL> Select s.sid, s.username,
  2         i.instance_name || '_ora_' || ltrim(to_char(p.spid)) ||
  3           decode (p.traceid, null, '', '_'||p.traceid) || '.trc'
  4           TraceFile
  5  from v$session s, v$process p, v$instance i
  6  where p.addr = s.paddr
  7    and s.type = 'USER' and s.username is not null
  8  order by username, sid
  9  /
       SID USERNAME                       TRACEFILE
---------- ------------------------------ ------------------------------
       149 MICHEL                         mika_ora_9312.trc
       150 MICHEL                         mika_ora_8884.trc
       151 MICHEL                         mika_ora_8224.trc

3 rows selected.