DOCSP 39098 Recommend limiting DDL operations during a sync (#311)

* DOCSP-39098 Recommend limiting DDL operations during a sync

* DOCSP-39098 ddl warning

* DOCSP-39098 ddl warning

* DOCSP-39098 ddl warning

* DOCSP-39098 tech edit

* DOCSP-39098 tech edit

Author: ltran-mdb2

source/reference/mongosync.txt

@@ -207,6 +207,19 @@ Even if documents move between source shards during replication,
 {+c2c-product-name+} maintains the :term:`eventual consistency`
 guarantee on the destination cluster.
 
+Data Definition Language (DDL) Operations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Using DDL operations (operations that act on collections or databases
+such as :method:`db.createCollection()` and :method:`db.dropDatabase()`)
+during sync increase the risk of migration failure and may negatively
+impact ``mongosync`` performance. For best performance, refrain from
+performing DDL operations on the source cluster while the sync is in
+progress.
+
+For more information on DDL operations, see
+:ref:`txn-prod-considerations-ddl`. 
+
 Views
 ~~~~~