Hello:
I get the following error while updating an element using NHibernate.

Unhandled Exception: NHibernate.ADOException: could not update: [TestHibernate.U
pdateISCM#164][SQL: UPDATE P_SSDB_DEPT SET VALUE = ? WHERE DEPT_ID = ?] ---> System.Data.OracleClient.OracleException: ORA-12571: TNS:packet writer failure

Mapping class:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="TestHibernate.UpdateISCM, TestHibernate"
table="P_SSDB_DEPT">
<id name="Id" column="DEPT_ID" type="String" length="10">
<generator class="assigned"/>
</id>
<property name="StatusFlag"
column="VALUE"
type="String"
length="128"/>
</class>
</hibernate-mapping>

Object Class file

using System;
using System.Collections.Generic;
using System.Text;

namespace TestHibernate
{
public class UpdateISCM
{
private string statusFlag;
private string id;

public UpdateISCM()
{

}

public virtual string Id
{
get { return id; }
set { id = value; }
}

public virtual string StatusFlag
{
get { return statusFlag; }
set { statusFlag = value; }
}
}
}

Test class

Configuration config = new Configuration();

config.SetProperty(NHibernate.Cfg.Environment.ConnectionProvider, "NHibernate.Connection.DriverConnectionProvider");
config.SetProperty(NHibernate.Cfg.Environment.Dialect, "NHibernate.Dialect.OracleDialect");
config.SetProperty(NHibernate.Cfg.Environment.ConnectionDriver, "NHibernate.Driver.OracleClientDriver");
config.SetProperty(NHibernate.Cfg.Environment.ConnectionString, "Data Source=source;User ID=abc;Password=abc;Unicode=True");

config.AddAssembly("TestHibernate");

ISessionFactory factory = config.BuildSessionFactory();
ISession session = factory.OpenSession();
//ITransaction transaction = session.BeginTransaction();

UpdateISCM joeCool = new UpdateISCM();
joeCool.Id = "164";
joeCool.StatusFlag ="Changed";
session.Update(joeCool);
session.Flush();
//transaction.Commit();
session.Close();

I don't know Oracle (anyone?) but just to help get things started for you: to what type of query problem might a "packet writer failure" refer?

Also, this is a really confusing use pattern of NH. Presumably, you already saved UpdateISCM["164"], and now you are updating it by building a whole new object with the same ID and calling Update()? Interesting, in that it saves you a read, but not something I've seen before.

I know this is three years old (ish), but I think I know the answer to the problem here. Given that it hasnt been posted here, I thought it may help others who get this problem.

Its down to the connection string. This version of Oracle, at least, has a fairly funky connection string if you are not using TNS. You can get the connection string from www.connectionstrings.com for both types of connection.

I hope replying to such an old post doesnt annoy anyone..