exernal table syntax

I am getting an error on the following:
CREATE TABLE rta.obd_po_data (po_number CHAR(8))   ORGANIZATION EXTERNAL
  (TYPE ORACLE_LOADER
   DEFAULT DIRECTORY f_temp_dir
   ACCESS PARAMETERS
 (FIELDS RTRIM
            (po_number (1:8) CHAR(8))
 NOLOGFILE
 )
   LOCATION ('obd_po_data.dat')
   )  

The table creates but fails when referenced.  

select * from rta.obd_po_data
*
ERROR at line 1:

ORA-29913: error in executing ODCIEXTTABLEOPEN callout
ORA-29400: data cartridge error
KUP-00554: error encountered while parsing access parameters
KUP-01005: syntax error: found "nologfile": expecting one of: "exit"
KUP-01007: at line 3 column 2
ORA-06512: at "SYS.ORACLE_LOADER", line 14
ORA-06512: at line 1

--
http://www.freelists.org/webpage/oracle-l