APEX

Good afternoon,
I have requested an official Oracle Apex workspace in order to have a look into 4.1. I made a small application with some dynamic action calls. I created a plsql call save some values in a table.

declare
  l_flag      smallint; 
  l_res_id    number := :P1_RESSOURCE;
  l_res_valid number := :P1_RES_VALID;
 
begin
  -- Ressourcen Name speichern wenn notwenig
  begin
    select 1 into l_flag 
    from oo_ressource 
    where nvl2(:P1_RESSOURCE,or_id,0) = nvl(:P1_RESSOURCE,0) 
      and nvl2(:P1_RESSOURCE,or_name,'') != :P1_RES_NAME 
      and length(:P1_RES_NAME)> 0;
    
    update oo_ressource set
      or_name = :P1_RES_NAME
    where or_id = l_res_id;
    
    if SQL%NOTFOUND then
      select tupel_seq.nextval into l_res_id from dual;
      insert into oo_ressource(or_id, or_name)
      values(l_res_id, :P1_RES_NAME);
    end if;
    commit;
  exception when others then
    null;
  end;

  --Zeitraum speichern
  update oo_res_valid set
    orv_from = :P1_RES_FROM,
    orv_to   = :P1_RES_TO
  where orv_id = l_res_valid;
  if SQL%NOTFOUND then
    select tupel_seq.nextval into l_res_valid from dual;
    insert into oo_res_valid(orv_id, orv_or_id, orv_from, orv_to)
    values(l_res_valid, l_res_id, :P1_RES_FROM, :P1_RES_TO);
  end if;
  commit;
    
  :P1_RESSOURCE := l_res_id;
  :P1_RES_VALID := l_res_valid; 
  
end;

If I click on the save button which executes the ajax call I receive the following error messages:
AJAX-Aufruf gab Serverfehler ORA-01950: keine Berechtigungen für Tablespace 'USERS' für PL/SQL-Code ausführen zurück.

Ajax call ORA-01950: no priviledge on tablespace USERS for PL/SQL code.

What kind of setting can I made to solve the problem ?

Many thanks.

brgds,
Birthe