2017-11-23 14:02:49,527 WARN  [org.jboss.jca.core.connectionmanager.pool.validator.ConnectionValidator] (ConnectionValidator) IJ000602: ConnectionValidator ignored unexpected runtime exception: java.lang.NullPointerException
        at java.util.concurrent.ConcurrentLinkedDeque.checkNotNull(ConcurrentLinkedDeque.java:798)
        at java.util.concurrent.ConcurrentLinkedDeque.linkLast(ConcurrentLinkedDeque.java:386)
        at java.util.concurrent.ConcurrentLinkedDeque.addLast(ConcurrentLinkedDeque.java:903)
        at org.jboss.jca.core.connectionmanager.pool.mcp.SemaphoreConcurrentLinkedDequeManagedConnectionPool.returnForFrequencyCheck(SemaphoreConcurrentLinkedDequeManagedConnectionPool.java:1597)
        at org.jboss.jca.core.connectionmanager.pool.mcp.SemaphoreConcurrentLinkedDequeManagedConnectionPool.validateConnections(SemaphoreConcurrentLinkedDequeManagedConnectionPool.java:1523)
        at org.jboss.jca.core.connectionmanager.pool.validator.ConnectionValidator$ConnectionValidatorRunner.run(ConnectionValidator.java:277)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)

    <datasource jndi-name="java:/DB1" pool-name="DB1" statistics-enabled="true">
        <connection-url>jdbc:oracle:thin:@ServerA:1521:DB1</connection-url>
        <driver-class&gt;oracle.jdbc.OracleDriver</driver-class&gt;
        <connection-property name="v$session.program">
            ServerA
        </connection-property>
        <driver>oracle</driver>
        <pool>
            <min-pool-size>490</min-pool-size>
            <initial-pool-size>490</initial-pool-size>
            <max-pool-size>490</max-pool-size>
            <prefill>true</prefill>
            <allow-multiple-users>false</allow-multiple-users>
        </pool>
        <security>
            <user-name>username</user-name>
            <password>password</password>
        </security>
        <validation>
            <check-valid-connection-sql>SELECT 1 FROM DUAL</check-valid-connection-sql>
            <validate-on-match>false</validate-on-match>
            <background-validation>true</background-validation>
            <background-validation-millis>120000</background-validation-millis>
        </validation>
        <timeout>
            <blocking-timeout-millis>3000</blocking-timeout-millis>
            <allocation-retry>10</allocation-retry>
            <allocation-retry-wait-millis>60000</allocation-retry-wait-millis>
        </timeout>
        <statement>
            <prepared-statement-cache-size>10</prepared-statement-cache-size>
        </statement>
    </datasource>