Oracle JDBC connection with Weblogic 10 datasource mapping, giving problem java.sql.SQLException: Closed Connection

I am using weblogic 10 JNDI datasource to create JDBC connections, below is my config

<?xml version="1.0" encoding="UTF-8"?>
<jdbc-data-source xmlns="http://www.bea.com/ns/weblogic/90" xmlns:sec="http://www.bea.com/ns/weblogic/90/security" xmlns:wls="http://www.bea.com/ns/weblogic/90/security/wls" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.bea.com/ns/weblogic/920 http://www.bea.com/ns/weblogic/920.xsd">
  <name>XL-Reference-DS</name>
  <jdbc-driver-params>
    <url>jdbc:oracle:oci:@abc.XL.COM</url>
    <driver-name>oracle.jdbc.driver.OracleDriver</driver-name>
    <properties>
      <property>
        <name>user</name>
        <value>DEV_260908</value>
      </property>
      <property>
        <name>password</name>
        <value>password</value>
      </property> 
      <property>
        <name>dll</name>
        <value>ocijdbc10</value>
      </property>
      <property>
        <name>protocol</name>
        <value>oci</value>
      </property> 
      <property>
        <name>oracle.jdbc.V8Compatible</name>
        <value>true</value>
      </property>
      <property>
        <name>baseDriverClass</name>
        <value>oracle.jdbc.driver.OracleDriver</value>
      </property>
    </properties>
  </jdbc-driver-params>
  <jdbc-connection-pool-params>
    <initial-capacity>1</initial-capacity>
    <max-capacity>100</max-capacity>
    <capacity-increment>1</capacity-increment>
    <test-connections-on-reserve>true</test-connections-on-reserve>
    <test-table-name>SQL SELECT 1 FROM DUAL</test-table-name>
  </jdbc-connection-pool-params>
  <jdbc-data-source-params>
    <jndi-name>ReferenceData</jndi-name>
    <global-transactions-protocol>OnePhaseCommit</global-transactions-protocol>
  </jdbc-data-source-params>
</jdbc-data-source>

When I run a bulk task where there are lots of connections made and closed, sometimes it gives connection closed exception for any of the task in the bulk task.

Below is detailed exception'

java.sql.SQLException: Closed Connection
 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111)
 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:145)
 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:207)
 at oracle.jdbc.driver.OracleStatement.ensureOpen(OracleStatement.java:3512)
 at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3265)
 at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:3367)

Any ideas?