anchor.diff:  %%--------------------------------------------------------------------
   handle_call({synchronize, FileCtx, Block, Prefetch, TransferId, Session}, From,
       #state{from_sessions = FS} = State0) ->
  -    {message_queue_len, QL} = erlang:process_info(self(), message_queue_len),
       State = State0#state{file_ctx = FileCtx},
       TransferId =/= undefined andalso (catch gproc:add_local_counter(TransferId, 1)),
       OverlappingInProgress = find_overlapping(Block, State),
  
positive.code:     Prefetch :: boolean(), #state{}) ->
      NewRequests :: [{block(), fetch_ref()}].
  start_transfers(InitialBlocks, TransferId, Prefetch, State) ->
      {LocationDocs, FileCtx2} = file_ctx:get_file_location_docs(State#state.file_ctx),
      ProvidersAndBlocks = replica_finder:get_blocks_for_sync(LocationDocs, InitialBlocks),
      FileGuid = State#state.file_guid,
      SpaceId = file_ctx:get_space_id_const(FileCtx2),
      DestStorageId = State#state.dest_storage_id,
      DestFileId = State#state.dest_file_id,
      Priority = case Prefetch of true -> high_priority; false ->
  
negative.code: init({_UserCtx, FileCtx}) ->
      fslogic_blocks:init_cache(),
      %% trigger creation of local file location
      FileGuid = file_ctx:get_guid_const(FileCtx),
      SpaceId = file_ctx:get_space_id_const(FileCtx),
      {DestStorageId, FileCtx2} = file_ctx:get_storage_id(FileCtx),
      {DestFileId, FileCtx3} = file_ctx:get_storage_file_id(FileCtx2),
      {ok, #state{file_ctx = FileCtx3,
          file_guid = FileGuid,
          space_id = SpaceId,
          dest_storage_id = DestStorageId,
  