Disable Parallel Query for Spesific User

Hi All,

I want to prevent a spesific user which is executing all select or dml querys parallel. (The user is executing all select * from table or update table queries parallely with /*+ PARALLEL(16) */ hints. And I need to prevent this situation.)

I have written below Logon Trigger but it doesn't work.

Can anyone help me what is problem or if it exists another solutions ?

create or replace trigger disable_parallel

after logon on <spesific_user_name>.schema

BEGIN

execute immediate 'ALTER SESSION DISABLE PARALLEL DML';

END;

/