ORA-02020: too many database links in use

select 'max open links'    text, to_number(value) value from v$parameter where name = 'open_links' union all
select 'actual open links' text, count(*) value from v$dblink;

begin
   for lnk in (select db_link from v$dblink) loop
       dbms_session.close_database_link(lnk.db_link);
   end loop;
end;
/