We are seeing a lot of the following errors in the catalina.out for our vibe servers

ERROR [http-8443-13] [org.hibernate.util.JDBCExceptionReporter] - Connection oracle.jdbc.driver.T4CConnection@df10abf is closed.

Is this normal? If not is it a java problem or oracle issue?

3 vibe 3.3 servers SLES 11SP2
2 indexing servers SLES 11 SP2
Java SDK 1.6.0_33
Oracle 11G RAC

thanks in advance