BUG: OpenSchema Method Generates Error 3251

ID: Q195487

The information in this article applies to:

ActiveX Data Objects (ADO), versions 1.5, 2.0, 2.01

SYMPTOMS

Using server-side cursors to open a recordset with OpenSchema, such as "Set rs = Connection.OpenSchema" generates error 3251:

   Application-defined or object-defined error.

CAUSE

Using the ActiveX Data Objects (ADO) OpenSchema method uses the IDBSchemaRowset interface to provide advanced schema information. This interface uses the GetRowset method to return a schema rowset. Currently, properties are not passed to the IDBSchemaRowset::GetRowset() when using a server-side cursor. This includes the IConnectionPointContainer property that is necessary for supporting notification (events). This results in ADO not hooking in the notification.

RESOLUTION

Open the connection on the client-side. For example:

   Set Connection.CursorLocation = adUseClient

This way the client engine passes the IConnectionPointContainer property, and ADO can hook in the notification.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

Use the following steps to reproduce this behavior using Visual Basic code:

1. Start a new Visual Basic project. Form1 is created by default.

2. Add a command button (Command1) to Form1. Change the name property to

   cmdOpenSchema.

3. Add the Microsoft ActiveX Data Objects 2.0 Library as a Reference.

4. Paste the following code in the General Declaration of Form1:

      Option Explicit
         Dim WithEvents rs_Events As ADODB.Recordset

      Private Sub cmdOpenSchema_Click()

         Dim cn As New ADODB.Connection

         On Error GoTo ErrHandler

         Set cn = New ADODB.Connection

        ' Uncomment the following line to workaround the problem:
        ' cn.CursorLocation = adUseClient

        ' Open connection
        cn.Open "Provider=MSDASQL;DSN=pubs;UID=sa;PWD=;Database=pubs;"

        ' Error 3251 occurs at the following line.
        Set rs_Events = cn.OpenSchema(adSchemaTables)

        ' As a test: Print all table names and types in your database.
        Do Until rs_Events.EOF
           Debug.Print "Table name: " & rs_Events!TABLE_NAME & _
              vbCr & "Table type: " & rs_Events!TABLE_TYPE & vbCr
          rs_Events.MoveNext
       Loop

      ' Clean up objects.
         rs_Events.Close
         cn.Close
         Set rs_Events = Nothing
         Set cn = Nothing

      Exit Sub

      ErrHandler:

          MsgBox Err.Number & ": " & Err.Description

      End Sub

5. Run the program. Notice that when the Cursorlocation property is set to

   adUseClient that all the information prints properly to the Immediate
   Window.

Additional query words:

Keywords          : kbADO200bug kbADO201bug 
Version           : WINDOWS:1.5,2.0,2.01
Platform          : WINDOWS
Issue type        : kbbug
Solution Type     : kbpending

Last Reviewed: November 10, 1998