Problems with Connection pool and Informix 11.5

Hi, We have IDS 9.40 and a web aplicattion with apache 2.0.53 and tomcat 5.5.26. We use a jdbc of informix 9.40 and a pool created with this iformix jdbc. When we close a connection, this is closed on the server. We are going to migrate to IDS 11.5 and we have substituted the jdbc 9.40 with the jdbc 11.5 and use the same pool (IBM Informix JBDC Driver/ Embedded SQL V3.50). Now, when we close a connection, this is not closed on the server and the server crashes later. This is the code we use to create the pool cpds = new IfxConnectionPoolDataSource(); cpds.setIfxCPMInitPoolSize(3); cpds.setIfxCPMMaxPoolSize(10); cpds.setIfxCPMMinPoolSize(5); cpds.setServerName("remoto"); cpds.setDatabaseName("bdprueba"); cpds.setIfxIFXHOST("192.168.161.122"); cpds.setPortNumber(1525); cpds.setUser("user"); cpds.setPassword("passwd"); cpds.setIfxCPMAgeLimit(100); cpds.setIfxIFX_ISOLATION_LEVEL("1"); cpds.setIfxIFX_AUTOFREE(true); This is the code we use to get a connection retorno = cpds.getPooledConnection().getConnection(); retorno.setTransactionIsolation(Connection.TRANSACTION_READ_UNCOMMITTED); This is the code we use to close a connection conexion.close(); Thanks!!