Hello Team,
Do anyone have any update on this. Please find the hbm below. 
I am opening and closing the session properly as per hibernate guide.
But this behaviour comes when number of inserts or updates increases.
Is it a problem with the jdbc driver?or hibernate?
Code:
<class name="com.t.d.sms.db.entity.InputMessage"
      table="SMSCP_INPUT_MESSAGE_TABLE">
      <id name="inputMessageId" column="INPUT_MESSAGE_ID">
         <generator class="sequence">
            <param name="sequence">
               SMSCP_INPMSGT_INP_MSG_ID_SEQ
            </param>
         </generator>
      </id>
      <property name="receivedTime" column="RECEIVED_TIME" />
      <property name="msisdn" column="MSISDN" />
      <property name="messageText" column="MESSAGE_TEXT" />
      <property name="correlationId" column="CORRELATION_ID" />
      <property name="processedFlag" column="PROCESSED_FLAG" />
      <property name="inputMsgStatus" column="INPUT_MSG_STATUS" />
      <property name="respondedTime" column="RESPONDED_TIME" />
      <property name="serviceNumber" column="SERVICE_NUMBER" />
   </class>