title: When does the replication from primary to secondary happen?
body: <p>I have setup a 3 node replica set.</p>
  
  <p>Writing to primary node works but when I read with <code>readPreference=secondary;</code> I get values as null. </p>
  
  <p>When I open the local node with robomongo I see that the collection does not exist. So it has not been replicated?</p>
  
  <p>I am not sure when it gets replicated or am I missing something?</p>
  
  <p><strong>Update</strong></p>
  
  <p>I have used the following URI</p>
  
  <p><code>mongodb://DNS1,DNS2,DNS3/?readPreference=secondary&amp;w=0</code></p>