anchor.diff:    %%   external format before saving in Tab2
     case lvl_get(Lvl2,Key2) of
       not_found -> via(Lvl1,[],Lvl2,Key2,false);
  -    Key1      -> via(Lvl1,mk_ekey(Key1),Lvl2,Key2,true)
  +    Key1      -> via(Lvl1,Key1,Lvl2,Key2,true)
     end.
   
   via(Lvl1,Key1,Lvl2,Key2,Retry) ->
  
positive.code:     #lvl{}    -> false
    end.
  
  delete_tab(S,Lvl = #lvl{}) ->
    get_rid_of(Lvl,S#state.keep_db),
    true;
  delete_tab(_,_) ->
    false.
  
  get_rid_of(Lvl,false) -> lvl_destroy(Lvl);
  get_rid_of(Lvl,true)  -> lvl_close(Lvl).
  
  siz(S) ->
    fold_lvl(S,fun(Lvl,O) -> [{Lvl#lvl.name,undefined}|O] end).
  
  key_getter(Lvl) ->
    Iter = lvl_iter(Lvl,keys_only),
  
negative.code:     lvl_close_iter(Iter)
    end.
  
  check_np(prev,invalid_iterator,Iter,_Key) ->
    %% lvl_mv_iter/2 moved the iterator to the first record after TK: in
    %% case of TK being the last record, it will return an
    %% invalid_iterator and we have to fix the situation here
    check_np(lvl_mv_iter(Iter,last));
  check_np(prev,{KeyNext,_},Iter,Key) when KeyNext >= Key ->
    %% lvl_mv_iter/2 moved the iterator to the first record not before
    %% TK: we are interested in the previous record, so an additional
    %% iterator step is necessary
    check_np(lvl_mv_iter(Iter,prev));
  check_np(next,{Key,_},Iter,Key) ->
    %% the requested key was in the table: an additional iterator step
    %% is necessary
    check_np(lvl_mv_iter(Iter,next));
  check_np(next,KV,_Iter,_Key) ->
    check_np(KV).
  
  check_np(invalid_iterator) -> end_of_table;
  check_np(KV) -> KV.
  
  deleter(Lvl,Key) ->
    case lvl_get(Lvl,Key) of
  