ORA-12899 error from function invoked from SQL*Loader

Question

I am getting the above error when I call a function from my SQL*Loader script, and I am not seeing what the problem is. As far as I can see, there should be no problem with the field lengths, unless the length of the automatic variable within my function is somehow being set at 30? Here are the details (in the SQL*Loader script, the field of interest is the last one):
====
Error:
====
Record 1: Rejected - Error on table TESTM8.LET_DRIVE_IN_FCLTY, column DIF_CSA_ID.
ORA-12899: value too large for column "TESTM8"."LET_DRIVE_IN_FCLTY"."DIF_CSA_ID" (actual: 30, maximum: 16)
=======
Function:
=======
CREATE OR REPLACE FUNCTION find_MCO_id (di_oid_in DECIMAL)
RETURN CHAR IS mco_id CHAR;
BEGIN
SELECT AOL_MCO_LOC_CD INTO mco_id
FROM CONV_DI_FLCTY
WHERE DIF_INST_ELMNT_OID = di_oid_in;
RETURN TRIM(mco_id);
END;
==============
SQL*Loader Script:
==============
LOAD DATA
INFILE 'LET_DRIVE_IN_FCLTY.TXT'
BADFILE 'LOGS\LET_DRIVE_IN_FCLTY_BADDATA.TXT'
DISCARDFILE 'LOGS\LET_DRIVE_IN_FCLTY_DISCARDDATA.TXT'
REPLACE
INTO TABLE TESTM8.LET_DRIVE_IN_FCLTY
FIELDS TERMINATED BY '~' OPTIONALLY ENCLOSED BY '"'
DIF_DRIVE_IN_OID DECIMAL EXTERNAL,
DIF_FCLTY_TYPE_OID DECIMAL EXTERNAL NULLIF DIF_FCLTY_TYPE_OID = 'NULL',
DIF_INST_ELMNT_OID DECIMAL EXTERNAL,
DIF_PRI_PERSON_OID DECIMAL EXTERNAL NULLIF DIF_PRI_PERSON_OID = 'NULL',
DIF_SEC_PERSON_OID DECIMAL EXTERNAL NULLIF DIF_SEC_PERSON_OID = 'NULL',
DIF_CREATE_TS TIMESTAMP "yyyy-mm-dd-hh24.mi.ss.ff6",
DIF_LAST_UPDATE_TS TIMESTAMP "yyyy-mm-dd-hh24.mi.ss.ff6",
DIF_ADP_ID CHAR NULLIF DIF_ADP_ID = 'NULL',
DIF_CAT_CLAIMS_IND CHAR,
DIF_CAT_DIF_IND CHAR,
DIF_DAYLT_SAVE_IND CHAR,
DIF_OPEN_PT_TM_IND CHAR,
DIF_CSA_ID CONSTANT "find_MCO_id(:DIF_DRIVE_IN_OID)"
============
Table Definitions:
============
SQL> describe CONV_DI_FLCTY;
Name Null? Type
DIF_INST_ELMNT_OID NOT NULL NUMBER(18)
AOL_MCO_LOC_CD NOT NULL VARCHAR2(3)
SQL> describe LET_DRIVE_IN_FCLTY;
Name Null? Type
DIF_DRIVE_IN_OID NOT NULL NUMBER(18)
DIF_INST_ELMNT_OID NOT NULL NUMBER(18)
DIF_FCLTY_TYPE_OID NUMBER(18)
DIF_ADP_ID VARCHAR2(10)
DIF_CAT_DIF_IND NOT NULL VARCHAR2(1)
DIF_CAT_CLAIMS_IND NOT NULL VARCHAR2(1)
DIF_CSA_ID VARCHAR2(16)
DIF_DAYLT_SAVE_IND NOT NULL VARCHAR2(1)
DIF_ORG_ENTY_ID VARCHAR2(16)
DIF_OPEN_PT_TM_IND NOT NULL VARCHAR2(1)
DIF_CREATE_TS NOT NULL DATE
DIF_LAST_UPDATE_TS NOT NULL DATE
DIF_ITM_FCL_MKT_ID NUMBER(18)
DIF_PRI_PERSON_OID NUMBER(18)
DIF_SEC_PERSON_OID NUMBER(18)
=========================
Thanks for any help with this one!

Answer 1

I changed one line of the function to:
RETURN CHAR IS mco_id VARCHAR2(16);
But I still get the same error:
ORA-12899: value too large for column "TESTM8"."LET_DRIVE_IN_FCLTY"."DIF_CSA_ID" (actual: 30, maximum: 16)
I just am not seeing what is being defined as 30 characters. Any ideas much appreciated!