ds.xml creates a database connection, how to handle and close this connection

<DataSource ID="GRID_DS" dataFormat="iscServer" serverType="sql" dataSourceVersion="1" dbName="Oracle" schema="TESTORA">
<operationBindings>
<operationBinding operationType="fetch">
<customSQL>

SELECT * FROM table

</customSQL>
</operationBinding>
</operationBindings>

<fields>
<field name="GR_PICTURE" type="image" align="center"/>
<field name="GR_FILE_FORMAT" type="image" align="center"/>
<field name="GR_XML_CHECK" type="integer" align="center"/>
<field name="GR_XML_DWND" type="link" align="center"/>
<field name="GR_CLIENT_NAME" type="text" align="center"/>
<field name="GR_DESCRIPTION" type="text" align="center"/>
</fields>
</DataSource>


this is my ds.xml.

We are observing, when we are fetching this grid a database connection is getting open in database and we have no control on it, even after closing the session it is remaining in open status.

We are using oracle database 10G.

Please give us an idea how can we handle it.

1. How isomorphic handle database connection from ds xml?
2. When that open connection get closed.

Environment:
SmartGwt 3.1
Gwt 2.4
Jdk 1.7.0_51
Oracle 10G