DOCS-426 socket exception when primary steps down

source/core/replica-set-elections.txt

@@ -78,9 +78,9 @@ If you have a three-member replica set, where every member has one
 vote, the set can elect a primary as long as two members can connect
 to each other. If two members are unavailable, the remaining
 member remains a :term:`secondary` because it cannot connect to a
-majority of the set's members.
-
-While there is no primary, clients cannot write to the replica set.
+majority of the set's members. If the remaining member is a
+:term:`primary` and two members become unavailable, the primary steps
+down and becomes and secondary.
 
 Network Partitions
 ~~~~~~~~~~~~~~~~~~

source/faq/diagnostics.txt

@@ -31,7 +31,7 @@ following commands:
    sudo grep mongod /var/log/messages
    sudo grep score /var/log/messages
 
-.. _faq-troubleshooting:
+.. _faq-keepalive:
 
 Does TCP ``keepalive`` time affect sharded clusters and replica sets?
 ---------------------------------------------------------------------

source/tutorial/troubleshoot-replica-sets.txt

@@ -177,6 +177,30 @@ Consider the following example of a bidirectional test of networking:
    and firewall configuration and reconfigure your environment to
    allow these connections.
 
+Socket Exceptions when Rebooting Secondaries Simultaneously
+-----------------------------------------------------------
+
+When you reboot members of a replica set, make sure the set keeps a
+majority of its votes available. When a set's active members can no
+longer form a majority, the set's :term:`primary` steps down and becomes
+a :term:`secondary`. The former primary closes all open connections to
+client applications. Clients attempting to write to the former primary
+receive socket exceptions and "Connection reset" errors.
+
+For example, if you have a three-member replica set where every member
+has one vote, the set can elect a primary only as long as two members
+can connect to each other. If two members become unavailable and the
+remaining member is a primary, the primary steps down and becomes a
+secondary.
+
+When a majority of votes is available, the set elects a primary
+and the errors cease.
+
+To avoid errors, reboot replica set member's one at a time.
+
+For more information on votes, see :doc:`/core/replica-set-elections`. For
+related information on connection errors, see :ref:`faq-keepalive`.
+
 .. _replica-set-troubleshooting-check-oplog-size:
 
 Check the Size of the Oplog