Microsoft KB Archive/177138

= INFO: Nested Transactions Not Available in ODBC/OLE DB/ADO =

Article ID: 177138

Article Last Modified on 12/5/2003

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APPLIES TO


 * Microsoft Data Access Components 1.5
 * Microsoft Data Access Components 2.0
 * Microsoft Data Access Components 2.1
 * Microsoft Data Access Components 2.5
 * Microsoft Data Access Components 2.6
 * Microsoft Data Access Components 2.7
 * Microsoft Data Access Components 2.8

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This article was previously published under Q177138



SUMMARY
Neither Open Database Connectivity (ODBC), nor Microsoft OLE DB Provider, supports Nested Transactions. ActiveX Data Objects (ADO) supports the feature, but only if the underlying provider exposes it. Currently only the Jet OLE DB provider supports Nested Transactions.



MORE INFORMATION
Neither ODBC, nor any released OLE DB Provider, exposes Nested Transaction functionality, even if the back-end data source supports this feature.

Nested Transactions are a feature of the Jet engine, but only when accessing the Jet engine directly via Data Access Objects (DAO). If using DAO against a Microsoft database (MDB) file that has an attached ODBC Data Source, any attempt to use nested transactions is ignored.

The ADO Help indicates that ADO supports nested transactions but only if the underlying OLE DB Provider supports nested transactions. The following Microsoft Providers do not support Nested Transactions: OLE DB Provider for ODBC Drivers

Index Server Provider for OLE DB

Active Directory Provider for OLE DB

Sample Code
Below is the error message and the code snippet that generates the error for ADO when the underlying provider does not support nested transactions:

Run-time error '-2147168237 (8004d013)':

Only one transaction can be active on this session.

Here is the code used to generate the error: Option Explicit Dim Cn As ADODB.Connection Dim Cmd1 As ADODB.Command Dim strConn, strQSQL As String

Private Sub Form_Load

' Open connection. Set Cn = New ADODB.Connection ' Change the connect string to match your setup strConn = "driver={SQL Server};server=MyServer;" & _ "uid= ;pwd= ;database=pubs" Set Cn = New ADODB.Connection Cn.Open strConn Cn.CursorLocation = adUseClient 'Cmd1 executes a SQL Insert strQSQL = "Insert INTO Stores (stor_id, stor_name, " & _  "stor_address, city) VALUES(?,?,?,?)" Set Cmd1 = New ADODB.Command With Cmd1 .ActiveConnection = Cn  .CommandText = strQSQL .CommandType = adCmdText .Parameters.Append .CreateParameter("", adChar, adParamInput, 4) .Parameters.Append .CreateParameter("", adVarChar, adParamInput, 40) .Parameters.Append .CreateParameter("", adVarChar, adParamInput, 40) .Parameters.Append .CreateParameter("", adVarChar, adParamInput, 20) End With End Sub

Private Sub cmdInsert_Click MousePointer = vbHourglass

Cn.BeginTrans

Cmd1(0) = "101" Cmd1(1) = "Store One" Cmd1(2) = "123 Oak St." Cmd1(3) = "Seattle" Cmd1.Execute

Cn.BeginTrans  'Comment out and this code will run and if you do so, 'Make sure that you delete the record that this sample 'adds to the database.

Cmd1(0) = "102" Cmd1(1) = "Store Two" Cmd1(2) = "123 Main St." Cmd1(3) = "Tacoma" Cmd1.Execute

Cn.CommitTrans  'Comment out and this code will run.

Cn.CommitTrans

MousePointer = vbDefault End Sub

Private Sub Form_Unload(Cancel As Integer) Cn.Close Set Cn = Nothing Set Cmd1 = Nothing

End Sub

