sqlplus dbms_output

Why I do not see the output of the following procedure in sqlplus??? As you see I execute serveroutput on command at beginnig but still it does not display the result, Please advise>

set serveroutput on
set serveroutput on size 200000
declare
begin

   for tab in (select table_name from user_tables where table_name = '\"BMA_Chemical\"')

      loop
             dbms_output.put_line(' create table


'||tab.table_name||'(');

             for col in (select column_name,data_type,data_length
             from user_tab_columns where table_name = tab.table_name)
                 loop
                       dbms_output.put_line(col.column_Name||'


'||col.data_type||' ('||col.data_length || '),');

                end loop;
     dbms_output.put_line('dummy date)'); 
      end loop;