begin
  for c_links in (select '@'||db_link as db_link from ALL_DB_LINKS)
  loop
    dbms_output.put_line('search for link: '||c_links.db_link);
    for c_source in (select * from all_source s
                      where s.text like '%'||c_links.db_link||'%')
    loop
      dbms_output.put_line('link '||c_links.db_link || 'is used in: ' || c_source.name);
    end loop;
  end loop;
end;