In multi-core, special dataDir is not used?

[Zhang, Lisheng]

Hi,
 
I am using solr 3.6.1, I created a new core "whatever3" dynamically, and I see 
solr.xml updated
as:
 
<solr persistent="true">
  <cores adminPath="/admin/cores" defaultCoreName="collection1">
    ...    
    <core name="whatever3" 
instanceDir="C:/lucene/Solr_3.6/apache-solr-3.6.1/example/mysolr\" 
dataDir="C:/lucene/Solr_3.6/apache-solr-3.6.1/example/mysolr/data/whatever3"/>
  </cores>
</solr>
 
But when I update data like 
http://localhost:8080/solr/whatever3/update?commit=true";, the data
did not go to the newly specified dataDir (I can see core "whatver3" is 
apparently used from log)?
 
Only way to make it work is NOT to define dataDir in solrconfig.xml, is this by 
design or I missed
sth?
 
Thanks very much for helps, Lisheng