Database Software

Hi all,
i have facinf this problem with DBMS_SCHEDULER.CREATE_JOB.

i am using windows 7 and oracle 11g r2 .

used this code to run batch file.

BEGIN  
   DBMS_SCHEDULER.CREATE_JOB (  
    job_name   => 'myjob',  
    job_type   => 'EXECUTABLE',  
    job_action  => 'c:\a.bat',  
    enabled   => false);  
 END; 

the i call it

EXEC  DBMS_SCHEDULER.RUN_JOB ('myjob');

or by this

DBMS_SCHEDULER.RUN_JOB ('myjob');

but this probelm occured

ERROR at line 1:
ORA-27369: job of type EXECUTABLE failed with exit code: Incorrect function.
ORA-06512: at "SYS.DBMS_ISCHED", line 185
ORA-06512: at "SYS.DBMS_SCHEDULER", line 486
ORA-06512: at line 1

FYI:
I also run the service that called
OracleJObSCHEDULER from windows service.

Is there any idea to solve this probelm?.