select r.value || '/' || lower(t.instance_name) || '_ora_'  
    || ltrim(to_char(p.spid)) || '.trc' trace_file          
from   v$process p, v$session s, v$parameter r, v$instance t
where  p.addr = s.paddr                                     
and    r.name = 'user_dump_dest'                            
and    s.sid = (select sid from v$mystat where rownum = 1) ;

