DOCS-246 counter edits

Author: Sam Kleinman

source/core/replication.txt

@@ -279,7 +279,7 @@ on the :term:`primary` and then records the operations on the primary's
 oplog. The :term:`secondary` members then replicate this log and apply
 the operations to themselves in an asynchronous process. All replica set
 members contain a copy of the oplog, allowing them to maintain the
-current state of the database. The oplog is an :term:`idempotent` log.
+current state of the database. Operations in the oplog are :term:`idempotent`.
 
 By default, the size of the oplog is as follows:
 
@@ -296,15 +296,16 @@ By default, the size of the oplog is as follows:
   the oplog.
 
 Before oplog creation, you can specify the size of your oplog with the
-:setting:`oplogSize` option. Once the oplog is created, you can only
-change the size of the oplog by using the :doc:`/tutorial/change-oplog-size` tutorial.
+:setting:`oplogSize` option. After you start a replica set member for
+the first time, you can only change the size of the oplog by using the
+:doc:`/tutorial/change-oplog-size` tutorial.
 
 In most cases, the default oplog size is sufficient. For example, if an
 oplog that is 5% of free disk space fills up in 24 hours of operations, then
 secondaries can stop copying entries from the oplog for 24 hours before
-they require full resyncing. This example describes a
-very high-volume member. In many circumstances, the default oplog can
-hold days of operations.
+they require full resyncing. However, most replica sets have much
+lower operation volumes, and their oplogs can hold a much larger
+number of operations.
 
 The following factors affect how MongoDB uses space in the oplog:
 

source/tutorial/change-oplog-size.txt

@@ -40,10 +40,18 @@ The examples in this procedure use the following configuration:
 - The replica set is running with a :setting:`data directory <dbpath>`
   of ``/srv/mongodb``.
 
-1. Shut down the current :term:`primary` instance in the replica set and
-   then restart it in "standalone" mode running on a different port.
-   Note that shutting down the primary will trigger a failover situation
-   and another member in the replica set will become primary.
+To change the size of the oplog for a replica set, use the following
+procedure for every member of the set that may become primary. 
+ 
+1. Shut down the :program:`mongod` instance and restart it in
+   "standalone" mode running on a different port.  
+
+   .. note:: 
+
+      Shutting down the :term:`primary` member of the set will trigger
+      a failover situation and another member in the replica set will
+      become primary. In most cases, it is least disruptive to modify
+      the oplogs of all the secondaries before modifying the primary.
 
    To shut down the current primary instance, use a command that
    resembles the following:
@@ -78,9 +86,9 @@ The examples in this procedure use the following configuration:
    a. In the :program:`mongo` shell, enter the following command to use the
       ``local`` database to interact with the oplog:
 
-   .. code-block:: javascript
+      .. code-block:: javascript
 
-      use local
+         use local
 
    #. Use the :method:`db.collection.save()` operation to save the last
       entry in the oplog to a temporary collection:
@@ -149,5 +157,5 @@ The examples in this procedure use the following configuration:
    set *and* if it has successfully "caught up," then it will likely
    become primary.
 
-#. Repeat this procedure for any other member of the replica set that
-   *could* become primary.
+#. Repeat this procedure for all other members of the replica set that
+   are or could become primary.