DOCSP-46986-destinationDataHandling-note (#598)

* DOCSP-46986-destinationDataHandling-note

* add additional info

* wording

* remove internal content

Author: amalhotra-mdb

source/reference/beta-program-private/many-to-one.txt

@@ -42,6 +42,17 @@ commands when starting :ref:`mongosync <c2c-mongosync>`:
 To start the sync operation between the source clusters and the
 destination cluster, see :ref:`c2c-quickstart-synchronize`.
 
+When beginning your sync operation for a many-to-one migration, add
+the following parameter to the :ref:`/start <c2c-api-start>` requests: 
+
+.. code:: 
+
+   "destinationDataHandling": "ignorePreExistingNamespaces"
+
+Setting ``"destinationDataHandling"`` to ``"ignorePreExistingNamespaces"`` 
+allows each migration to write to the destination cluster that may have 
+pre-existing namespaces from the other many-to-one migrations.
+
 Behavior 
 --------