Private Sub Command1_Click()
    
   Dim cmd As ADODB.Command
   Set cmd = New ADODB.Command
    
   Dim cn As ADODB.Connection
   Set cn = New ADODB.Connection
   With cn
      .ConnectionString = "Provider=MSDAORA.1;User ID=Demo;Data Source=<your oracle server alias>;Persist Security Info=False;password=demo"
      'Uncomment the following line to make this work.
      '.ConnectionString = "Provider=MSDASQL;User ID=Demo;Data Source=<your datasource name>;Persist Security Info=False;password=demo"
       .ConnectionTimeout = 10
       .CursorLocation = adUseClient
       .Open
   End With
    
   'Create the stored procedure for testing.
   Set cmd.ActiveConnection = cn
   With cmd
       .CommandType = adCmdText
       .CommandText = "Create or Replace Procedure TEST " & _
                      " (inParam in  varchar2," & _
                      " outParam out varchar2)" & _
                      " is " & _
                      " begin " & _
                      " outParam:= inParam;" & _
                      " end ;"

   End With
   cmd.Execute
    
   Debug.Print "Stored Proc Created"
    
   Set cmd = Nothing
   Set cmd = New ADODB.Command
   With cmd
        Set .ActiveConnection = cn
        .CommandType = adCmdStoredProc
        .CommandText = "TEST"
        .Parameters.Append .CreateParameter("inParam", adLongVarChar, adParamInput, 5000, String(4002, "c"))  '<<4001 works , 4002 fails
        .Parameters.Append .CreateParameter("outParam", adLongVarChar, adParamOutput, 5000, "")
        .Execute  '<<fails here with the Oracle OLEDB provider
           
    End With
    Debug.Print i & "   Output Parameter: " & Len(cmd(1).Value)

End Sub