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

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

* JP nit

* ED nit

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
@@ -64,6 +66,13 @@ the following changes that mimic the sync finalization process of the
        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-write-blocking:
 
 Write blocking