vpd and column masking

Hi
This is my first attempt to use vpd and column masking. So pardon me if this is a very stupid mistake. I am trying to do this but this is not working..

create or replace function sec_function_papf(p_object_schema IN VARCHAR2,  p_object_name VARCHAR2)
return varchar2
as
p_nid varchar2(200);
whoami varchar2(100);
begin
 select SYS_CONTEXT('userenv', 'SESSION_USER') into whoami from dual; if whoami = 'APPS'
then
p_nid := 'national_identifier = national_identifier'; return (p_nid);
else
p_nid := '1=2';
return (p_nid);
end if;
end;

BEGIN
     DBMS_RLS.ADD_POLICY(object_schema=>'APPS', object_name=>'PER_ALL_PEOPLE_F',

                         policy_name=>'PAPF_POLICY',
function_schema=>'APPS',
                         policy_function=>'SEC_FUNCTION_PAPF',
                         sec_relevant_cols=>'national_identifier',
                         sec_relevant_cols_opt=>dbms_rls.ALL_ROWS);

ORA-28104: input value for sec_relevant_cols is not valid
ORA-06512: at "SYS.DBMS_RLS", line 20
ORA-06512: at line 2

The problem is not with the value that I pass to sec_relevant_cols. Even if I remove that I get the error on the other parameters.

The function is created ok. I want to display ssn for privileged user otherwise display null values for other users but display the user's own ssn.

Any pointers on what is not right here?

Thank you
- kumar

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