SQL & PL/SQL

Hi all,
I want script of DDL of all tables in Database not in particular schema,
As I am using below query
SELECT DBMS_METADATA.GET_DDL('TABLE',u.table_name)
FROM ALL_TABLES u
WHERE u.nested='NO'
AND (u.iot_type is null or u.iot_type='IOT')

but it gives error as below.
ORA-31603: object "ICOL$" of type TABLE not found in schema "SCOTT"
It should give DDL of all tables, also I am not having DBA Privs.

Please help me.

Thanks & Regards
Rajiv.