test-connections-on-reserve

If you get:

java.sql.SQLException: Protocol violation: [ 0, ] at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:536)
java.sql.SQLRecoverableException: Closed Connection at oracle.jdbc.driver.PhysicalConnection.needLine(PhysicalConnection.java:4220) at oracle.jdbc.driver.T4CXAResource.doStart(T4CXAResource.java:187)

then make sure that /jdbc-data-source/jdbc-connection-pool-params/test-connections-on-reserve is set to true