I start a trace but the file does not appear.

I started the trace with command:

EXECUTE DBMS_SYSTEM.set_sql_trace_in_session(sid=>395, serial#=>62633, sql_trace=>TRUE);

When I execute the query:

select a.sid, a.serial#, a.username, a.sql_trace, b.spid

from v$session a, v$process b

where a.sql_trace != 'DISABLED' and b.addr = a.paddr;

The result is:

SID   SERIAL#   USERNAME  SQL_TRACE   SPID

395    62633        <user>           ENABLED       221580

But in diag\rdbms\<instance_name>\<instance_name>\trace, I don't see the file: <instance_name>_ora_221580.trc