Find Trace File
find trace file

http://www.builder.com.cn/2007/0910/497699.shtml

-- under 11g
SELECT    a.VALUE || b.symbol || c.instance_name || '_ora_' || d.spid || '.trc' trace_file
  FROM (SELECT VALUE FROM v$parameter WHERE NAME = 'user_dump_dest') a,
       (SELECT SUBSTR (VALUE, -6, 1) symbol FROM v$parameter
         WHERE NAME = 'user_dump_dest') b,
       (SELECT instance_name FROM v$instance) c,
       (SELECT spid FROM v$session s, v$process p, v$mystat m
         WHERE s.paddr = p.addr AND s.SID = m.SID AND m.statistic# = 0) d
;
-- after 11g
SELECT VALUE FROM V$DIAG_INFO WHERE NAME = 'Default Trace File';