Problem connecting to DataBase : java.sql.SQLRecoverableException: ORA-00028: your session has been killed

Issue

• We are receiving the following Exception on different JBoss instances from time to time and we don't understand what is causing this behavior.

2015-03-12 05:38:29,419ERROR[TestServiceImpl](Timer-2)Exception dans test(): java.sql.SQLRecoverableException: ORA-00028: your session has been killed

    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:447)
    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:396)
    at oracle.jdbc.driver.T4C8Oall.processError(T4C8Oall.java:951)
    at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:513)
    at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:227)
    at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:531)
    at oracle.jdbc.driver.T4CStatement.doOall8(T4CStatement.java:195)
    at oracle.jdbc.driver.T4CStatement.executeForRows(T4CStatement.java:1036)
    at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1336)
    at oracle.jdbc.driver.OracleStatement.executeUpdateInternal(OracleStatement.java:1845)
    at oracle.jdbc.driver.OracleStatement.executeUpdate(OracleStatement.java:1810)
    at oracle.jdbc.driver.OracleStatementWrapper.executeUpdate(OracleStatementWrapper.java:294)
    at org.jboss.jca.adapters.jdbc.WrappedStatement.executeUpdate(WrappedStatement.java:375)
    at TestServiceImpl.test(TestServiceImpl.java:262) [test.jar:]
    at java.util.TimerThread.mainLoop(Timer.java:555) [rt.jar:1.7.0_45]
    at java.util.TimerThread.run(Timer.java:505) [rt.jar:1.7.0_45]

• Here is how the datasource is defined:

 <datasource jta="false" jndi-name="java:/jdbc/testDS" pool-name="xxxx" enabled="true" use-ccm="false">
                    <connection-url>xxxxxxxxx</connection-url>
                    <driver-class>oracle.jdbc.OracleDriver</driver-class>
                    <driver>OracleJDBCDriver</driver>
                    <pool>
                        <min-pool-size>10</min-pool-size>
                        <max-pool-size>20</max-pool-size>
                        <prefill>true</prefill>
                    </pool>
                    <security>
                        <user-name>xxx</user-name>
                        <password>xxx</password>
                    </security>
                    <validation>
                        <check-valid-connection-sql>select 1 from dual</check-valid-connection-sql>
                        <validate-on-match>false</validate-on-match>
                        <background-validation>false</background-validation>
                    </validation>
                    <timeout>
                        <blocking-timeout-millis>30000</blocking-timeout-millis>
                        <idle-timeout-minutes>30</idle-timeout-minutes>
                    </timeout>
                    <statement>
                        <share-prepared-statements>false</share-prepared-statements>
                    </statement>
                </datasource>

• Do we need to remove from dual from <check-valid-connection-sql>Select 1 from dual</check-valid-connection-sql>?
• What is the impact of removing <idle-timeout-minutes>30</idle-timeout-minutes>?
• Is it better to activate <background-validation> and keep <validate-on-match> to false?