.. include:: ../../../03-exports/aliases.include
.. include:: ../../../03-exports/aliases-api.include

.. _use-case-tcp-multicast:

Large Data Mode
===============

The following snippets show how to configure *Fast DDS* |DomainParticipants| to run the
:ref:`PDP discovery<disc_phases>` phase over UDP multicast and communicate application data over a
:ref:`transport_tcp_tcp` or :ref:`transport_sharedMemory_sharedMemory`, which is called the ``LARGE_DATA``
configuration (See :ref:`rtps_layer_builtin_transports`).
With this approach, applications managing large samples can benefit from transmitting their data over TCP or SHM,
while at the same time have the flexibility of automatic discovery.
The ``LARGE_DATA`` mode can be set using the ``FASTDDS_BUILTIN_TRANSPORTS`` environment variable
(see :ref:`env_vars_builtin_transports`), XML profiles or via code.

.. tabs::

   .. tab:: Environment Variable

      .. code-block:: bash

         export FASTDDS_BUILTIN_TRANSPORTS=LARGE_DATA

   .. tab:: XML

      .. literalinclude:: /../code/XMLTester.xml
         :language: xml
         :start-after: <!-->LARGE_DATA_BUILTIN_TRANSPORTS<-->
         :end-before: <!--><-->
         :lines: 2-4, 6-13, 15-16

   .. tab:: C++

      .. literalinclude:: ../../../../code/DDSCodeTester.cpp
         :language: c++
         :dedent: 8
         :start-after: //LARGE_DATA_BUILTIN_TRANSPORTS
         :end-before: //!

.. note::
   ``LARGE_DATA`` configuration of the builtin transports will also create a SHM transport along the UDP and TCP
   transports. Shared Memory will be used whenever it is possible. Manual configuration will be required if a TCP
   communication is required when SHM is feasible.

   .. tabs::

      .. tab:: C++

         .. literalinclude:: ../../../../code/DDSCodeTester.cpp
            :language: c++
            :dedent: 8
            :start-after: //PDP-MULTICAST-DATA-TCP
            :end-before: //!

      .. tab:: XML

         .. literalinclude:: /../code/XMLTester.xml
            :language: xml
            :start-after: <!-->PDP-MULTICAST-DATA-TCP<-->
            :end-before: <!--><-->
            :lines: 2-4, 6-80, 82-83