I'm facing a problem of upgrading Hibernate 3 connected to Oracle 9i
to:
Hibernate 3 (no changes in Hibernate) connected to Oracle11g RAC. I'm using

My connection string:
jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=xxxxxxxxxxxxx.it)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=mysid)))

I've put Oracle10gDialect in the Hibernate.cfg.xml file.
I've got the error when I'm trying to connect:

java.sql.SQLException: Eccezione IO: Connection refused(DESCRIPTION=(ERR=1153)(VSNNUM=186647296)(ERROR_STACK=(ERROR=(CODE=1153)(EMFI=4)(ARGS='(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=10.197.65.111)(PORT=1521))(CONNECT_DATA=(CID=(PROGRAM=)(HOST=__jdbc__)(USER=))null))'))(ERROR=(CODE=303)(EMFI=1))))
oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:134)
oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:179)
oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:333)
oracle.jdbc.driver.OracleConnection.<init>(OracleConnection.java:404)
oracle.jdbc.driver.OracleDriver.getConnectionInstance(OracleDriver.java:468)
oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:314)
java.sql.DriverManager.getConnection(Unknown Source)
java.sql.DriverManager.getConnection(Unknown Source)
org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:110)
org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:423)
org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:119)
org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:57)
org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1326)
it.netsphere.hibernate.HibernateUtil.beginTransaction(HibernateUtil.java:143)
it.netsphere.hibernate.HibernateSessionRequestFilter.doFilter(HibernateSessionRequestFilter.java:27)

I've put the ojdbc6.jar, and the orai18n.jar.
I'm using jdk 1.5
Can anyone suggest me the solution ? I've client Oracle 11 installed on the machine.