Oracle Database Discussions

Is there any reason why trace file is not generated when using this command ?

begin
DBMS_SCHEDULER.CREATE_JOB(
job_name => 'COLCO_TEST',
job_type => 'PLSQL_BLOCK',
job_action => 'BEGIN DBMS_SESSION.SESSION_TRACE_ENABLE(TRUE, TRUE); END;',
enabled => TRUE,
start_date => NULL
);
end;
/

Job runs successfully but no trace file is generated.
If DBMS_SESSION.SESSION_TRACE_ENABLE(TRUE, TRUE); is called in sqlplus trace file is generated.

Any ideas ?

Thanks