DOCSP-40742-disaster-recovery-page-updates (#340) (#342)

* DOCSP-40742-disaster-recovery-page-updates (#340)

* DOCSP-40742-disaster-recovery-page-updates

* JP nit

* ED nit

* *

* build errors

* build errors

Author: ajhuh-mdb

source/reference/disaster-recovery.txt

@@ -15,9 +15,11 @@ Use ``mongosync`` for Disaster Recovery
 Setting up {+c2c-product-name+} to prepare for disaster recovery follows the 
 same procedure as other :ref:`connections <c2c-connecting>` between clusters.
 Synchronization keeps the destination cluster up to date with the source
-cluster and ready as a backup. In the event that the source cluster fails or
-becomes otherwise unavailable, the destination cluster can replace it as the
-primary cluster.
+cluster using :term:`eventual consistency`. This means that until the migration 
+commits, the destination cluster might represent a stale and inconsistent 
+version of the source cluster. If the source cluster fails or becomes otherwise 
+unavailable, the destination cluster can replace it as the primary cluster if 
+your application can tolerate potentially stale data.
 
 :program:`mongosync` temporarily alters some collection characteristics
 during synchronization. The original values are restored during the
@@ -58,6 +60,16 @@ the following changes that mimic the sync finalization process of the
 
        If synchronization was started with write blocking, disable the Write
        Block Mode.
+   * - :ref:`Capped Collections <c2c-dr-capped-collections>`
+     - Synchronization sets capped collections to the maximum allowable
+       size. To set your required maximum size, use the
+       :dbcommand:`collMod` command.
+   * - Dummy Indexes 
+     - In some cases, synchronization may create dummy indexes on the 
+       destination to support writes on sharded or collated collections. 
+
+       Use the :dbcommand:`dropIndexes` command to drop any dummy indexes. Each 
+       dummy index's name contains the word ``dummy``.
 
 
 .. _c2c-dr-unique:
@@ -141,3 +153,22 @@ To enable writes, update :dbcommand:`setUserWriteBlockMode`:
        }
    )
 
+.. _c2c-dr-capped-collections:
+
+Capped Collections
+------------------
+
+During synchronization, capped collections are set to the maximum
+allowable size. To set your required maximum size, use the ``collMod``
+command. For details, see :ref:`resize-capped-collection`.
+
+.. example:: 
+
+   .. code-block:: javascript
+      :emphasize-lines: 3
+
+      db.runCommand( {
+        collMod: "<collection_name>",
+        cappedSize: <max_size_in_bytes>,
+        cappedMax: <max_number_of_documents_in_collection>
+      } )