DBMS_SCHEDULER.run_job problem

 Hi  friends.I have one problem. I use Oracle 10g(r2) in oracle enter.server. Also I can execute backupdb.sh script from terminal success.But I created Job sheduler as

BEGIN
DBMS_SCHEDULER.CREATE_JOB
(
 job_name                    => 'BACKUP_DB_JOB',
 job_type                      => 'EXECUTABLE',
 job_action       => '/orahome/orastart/./backupdb.sh',
 start_date        => '13-jan-2010 6:32 PM',
 repeat_interval => 'FREQ=DAILY'
);
END;

although  i execute following

begin
  DBMS_SCHEDULER.run_job  (job_name=>'BACKUP_DB_JOB');
end;

then occur error [1]: (Error): ORA-27369: job of type EXECUTABLE failed with exit code: 274660 ORA-06512: at "SYS.DBMS_ISCHED", line 150 ORA-06512: at "SYS.DBMS_SCHEDULER", line 441 ORA-06512: at line 4