DOCSP-47126 edited oplog background fact (#609)

Author: sonderdonk-mdb

source/includes/fact-oplog-background.rst

@@ -1,19 +1,14 @@
 
 ``mongosync`` applies operations in the ``oplog`` on the source cluster
-to the data on the destination cluster.  When operations 
-that ``mongosync`` has not applied roll off the ``oplog`` 
+to the data on the destination cluster after the 
+:ref:`collection copy <c2c-collection-copy>` phase.  When 
+operations that ``mongosync`` has not applied roll off the ``oplog`` 
 on the source cluster, the sync fails and ``mongosync`` exits.
 
 .. note::
 
    .. include:: /includes/fact-applyOps.rst
 
-During the initial sync, ``mongosync`` may apply operations at a slower
-rate due to copying documents concurrently.
-After the initial sync, ``mongosync`` applies changes 
-faster and is more likely to maintain a position in the ``oplog``
-that is close to the real-time writes occurring on the source cluster.
-
 If you anticipate syncing a large data set, or if you plan to pause
 synchronization for an extended period of time, you might exceed the
 :term:`oplog window`. Use the :setting:`~replication.oplogSizeMB` setting