var 
  gHndFile, gHndMapedFile : HWND;
  gPntMapFile : Pointer;

procedure refreshData(str: string);
var
  fileName : string;
  f : TextFile;
  byteWrt : Cardinal;
  pStr : PAnsiChar;
begin
  fileName := 'myfile';
  gHndMapedFile:=CreateFileMapping(INVALID_HANDLE_VALUE,                
                                nil,                 
                                PAGE_READWRITE,       
                                0,                    
                                Length(str) * SizeOf(Char), 
                                PChar(fileName));        


  if gHndMapedFile = INVALID_HANDLE_VALUE then
  begin
    ShowMessage('Ошибка ' + SysErrorMessage(GetLastError));
    CloseHandle(gHndFile);
    Exit;
  end;

  pStr := PChar(str);
  WriteFile(gHndMapedFile, pStr, Length(str)*SizeOf(Char), byteWrt, nil);

  gPntMapFile:=MapViewOfFile(gHndMapedFile,           
                          FILE_MAP_ALL_ACCESS,  
                          0,0,
                          Length(str) * SizeOf(Char));
  if gPntMapFile=nil then
  begin
    ShowMessage('Ошибка '+SysErrorMessage(GetLastError));
    CloseHandle(gHndMapedFile);
    CloseHandle(gHndFile);
    Exit;
  end;
end;

refreshData('data');

procedure TfrmClient.btnReadClick(Sender: TObject);
var
  hMapedFile:HWND;
  pMapFile:Pointer;
const
  bufSize=100;// размер буффера
begin
  hMapedFile:=OpenFileMapping(FILE_MAP_ALL_ACCESS, 
                              False, 
                              PChar('myfile'));

  if hMapedFile=INVALID_HANDLE_VALUE then
  begin
    ShowMessage('Ошибка '+SysErrorMessage(GetLastError));
    Exit;
  end;

  pMapFile:=MapViewOfFile(hMapedFile,
                          FILE_MAP_ALL_ACCESS,
                          0,0,
                          bufSize*SizeOf(Char));

  if pMapFile=nil then
  begin
    ShowMessage('Ошибка '+SysErrorMessage(GetLastError));
    CloseHandle(hMapedFile);
    Exit;
  end;

  Memo1.Text:=PChar(pMapFile);
  UnmapViewOfFile(pMapFile);
  CloseHandle(hMapedFile);
end;