DOCSP-45860-older-version-limitations

source/includes/fact-older-version-limitations.rst

@@ -0,0 +1,46 @@
+- Writes that produce :term:`DDL <DDL (Data Definition Language)>` events cannot 
+  occur on the source cluster during the migration. The following events cannot 
+  occur: 
+
+  - ``collMod``
+  - ``create``
+  - ``createIndexes``
+  - ``drop``
+  - ``dropDatabase``
+  - ``dropIndexes``
+  - ``refineCollectionShardKey``  
+  - ``rename``
+  - ``reshardCollection``
+  - ``shardCollection``
+
+  This includes operations that may create new collections such as 
+  :dbcommand:`mapReduce`, :pipeline:`$out`, and :pipeline:`$merge`. This also 
+  includes collections created implicitly from inserts. Only writes that produce 
+  CRUD events can occur during the migration.
+
+  .. note:: 
+
+     Writes that produce DDL events on source collections outside of the 
+     :ref:`namespace filter <c2c-filtered-sync>` are allowed.
+
+- ``geoHaystack`` indexes are not supported.
+
+- :ref:`/reverse <c2c-api-reverse>` endpoint is not supported. You can't 
+  enable the ``reversible`` option in the :ref:`/start <c2c-api-start>` request.
+
+- You can't enable the ``enableUserWriteBlocking`` option in the ``/start`` 
+  request. Ensure that no writes are made to the source or destination cluster 
+  during the migration.
+
+- You can't enable the ``createSupportingIndexes`` :ref:`sharding parameter 
+  <c2c-api-start-sharding>`. Instead, create an index to support your shard key 
+  on the source cluster. 
+
+- If there are any indexes with inconsistent specs or that are missing 
+  ``mongosync`` returns an error. To check for index inconsistencies, see 
+  :ref:`manage-indexes-find-inconsistent-indexes`.
+
+- For source clusters running MongoDB 4.4, :ref:`SRV connection strings 
+  <connections-dns-seedlist>` are not supported. You must use a 
+  :ref:`standard connection string 
+  <connections-standard-connection-string-format>`.

source/reference/limitations.txt

@@ -115,7 +115,7 @@ Sharded Clusters
 - Shards cannot be added or removed while syncing.
 - ``mongosync`` only syncs indexes that exist on all shards.
 - ``mongosync`` only syncs indexes that have consistent index
-  specifications on all shards.
+  specifications on all shards. 
 
   .. note::
 
@@ -198,3 +198,13 @@ cluster.
 
 .. include:: /includes/fact-verifier-limitations
 
+Pre-6.0 Migrations 
+------------------
+
+Starting in 1.10, ``mongosync`` supports migrations from source clusters running 
+MongoDB server versions older than 6.0. For information on supported migration 
+paths, see :ref:`c2c-server-version-compatibility`.
+
+The following limitations apply to pre-6.0 migrations:
+
+.. include:: /includes/fact-older-version-limitations.rst