FIX: You receive an "ORA-01012" error message when you connect to an Oracle database by using MSDAORA

Steps to reproduce the behavior

1. Start Microsoft Visual Studio .NET.
2. On the File menu, point to
   New, and then click Project. The New Project dialog box appears.
3. Under Project Types, click Visual Basic Projects, and then click Console Applicationunder Templates.
4. In the Name box, type
   MyApp, and then click OK. By default, the Module1.vb file is created.
   
   If you are using Microsoft Visual C# .NET, the Class1.cs file is created.
5. Add the following code at the top:
   
   Microsoft Visual Basic .NET code

   Imports System
   Imports System.Data.OleDb

   Visual C# .NET code

   using System.Data.OleDb;

6. Add the following code to the Mainprocedure:
   
   Visual Basic .NET code

   Dim cn As OleDbConnection
   Dim cmd As OleDbCommand
   Dim r As OleDbDataReader
   Dim sid As String
   Dim orlcmd As String
   Dim connString As String = "Provider=MSDAORA;DataSource=<data source>;User ID=<user name>;Password=<password>;"
   Try
       'Create a new connection to the Oracle database by using MSDAORA.
       cn = New OleDbConnection
       cn.ConnectionString = connString
       cn.Open()
       cmd = New OleDbCommand
       cmd.CommandText = "SELECT SID , SERIAL# FROM V$SESSION WHERE SID = (SELECT SID FROM V$MYSTAT WHERE ROWNUM=1)"
       cmd.Connection = cn
       r = cmd.ExecuteReader()
       sid = ""
       If (r.Read()) Then
           sid = r.GetValue(0).ToString() + "," + r.GetValue(1).ToString()
       End If
       orlcmd = "Alter System Kill Session '" + sid + "' Immediate;"
       Console.WriteLine("Open the SQL Plus window, run the following command, and then press ENTER:")
       Console.WriteLine(orlcmd)
       Console.ReadLine()
       r.Close()
       cmd.CommandText = "SELECT count(*) from TAB"
       Try
           'Expecting this command to fail because connection has been killed
           r = cmd.ExecuteReader()
       Catch orlex As OleDbException
           Console.WriteLine(orlex.Message)
           cmd.Dispose()
           'Close the bad connection.
           cn.Close()
           System.Threading.Thread.Sleep(1000)
           cn.ConnectionString = connString
           cn.Open()
           cmd = New OleDbCommand
           cmd.CommandText = "SELECT count(*) FROM TAB"
           cmd.Connection = cn
           'This command will fail, but it will work when a new connection is used.
           r = cmd.ExecuteReader()
           If (r.Read()) Then
               Console.WriteLine(r.GetValue(0))
           End If
      End Try
   Catch ex As OleDbException
      Console.WriteLine(ex.ToString())
   End Try
   Console.WriteLine("Press ENTER to exit...")
   Console.ReadLine()
   

   Visual C# .NET code

   OleDbConnection cn;
   OleDbCommand cmd;
   OleDbDataReader r;
   String sid;
   String orlcmd;
   String connString="Provider=MSDAORA;DataSource=<data source>;User ID=<user name>;Password=<password>;";
   try
   {
       //Create a connection to the Oracle database by using MSDAORA.
       cn= new OleDbConnection();
       cn.ConnectionString=connString;
       cn.Open();
       cmd=new OleDbCommand();
       cmd.CommandText="SELECT SID , SERIAL# FROM V$SESSION WHERE SID = (SELECT SID FROM V$MYSTAT WHERE ROWNUM=1)";
       cmd.Connection=cn;
       r=cmd.ExecuteReader();
       sid="";
       if(r.Read())
       {
          sid=r.GetValue(0).ToString()+","+r.GetValue(1).ToString();
       }
       orlcmd="Alter System Kill Session '"+sid+"' Immediate;";
       Console.WriteLine("Open the SQL Plus window, run the following command, and then press ENTER:");
       Console.WriteLine(orlcmd);
       Console.ReadLine();
       r.Close();
       cmd.CommandText="SELECT count(*) from TAB";
       try
       {
           //Expecting this to fail because the connection is killed.
           r=cmd.ExecuteReader();
       }
       catch(OleDbException orlex)
       {
           Console.WriteLine(orlex.Message);
           cmd.Dispose();
           //Close the bad connection.
           cn.Close();
           System.Threading.Thread.Sleep(1000);
           cn.ConnectionString=connString;
           cn.Open();
           cmd=new OleDbCommand();
           cmd.CommandText="SELECT count(*) FROM TAB";
           cmd.Connection=cn;
           //This command will fail, but it will work when a new connection is used.
           r=cmd.ExecuteReader();
           if(r.Read())
           {
              Console.WriteLine(r.GetValue(0).ToString());
           }
       }
   }
   catch(OleDbException ex)
   {
       Console.WriteLine(ex.ToString());
   }
   Console.WriteLine("Press ENTER to exit...");
   Console.ReadLine();
   

   Note Modify the connection string according to your environment.
7. On the Build menu, click Build Solution.
8. On the Debug menu, click
   Start. You see that a command is displayed in the console window.
9. In Oracle SQL*Plus, run the command that is displayed in the console window.
10. Press ENTER. In the console window, you see the exception that is mentioned in the "Symptoms" section.