Hello

I work with oracle 8.1.7 and I wrote the following procedure

CREATE OR REPLACE PROCEDURE SetPointDeleted (
PointFeatureTable VARCHAR2, PunktFID NUMBER, MutID NUMBER)
AS
OS_User4Char VARCHAR2(6);
aStatement VARCHAR(500);
...
BEGIN
SELECT sys_context('userenv', 'os_user') INTO OS_User4Char FROM dual;
...
aStatement := 'update '||T_geo||' LG set LG.deleted = 1,
LG.mutation_id_deleted = '||MutID||',
LG.mutation_status_deleted = 3,
LG.user_deleted = '||OS_User4Char||',
LG.date_deleted = SYSDATE
where LG.deleted = 0 and exists (
select 1
from '||T||' L
where L.fid = '||FID_T||' and L.gid = LG.gid)';
EXECUTE IMMEDIATE aStatement;
...
END;
/
SHOW ERRORS;
COMMIT;

It is compiled successfully, but if I execute it, I get the message:
ErrorMessage : ORA-00904:

The column OS_User4Char does not exists ! How can I embed the value of
OS_User4Char which contents for example 'mere' in the String 'aStatement' ?
Thank you for help.