How to use DTS with custom ATL OLE-DB providers in Visual C++ 6.0 (241241)


The information in this article applies to:

  • Microsoft Visual C++, 32-bit Enterprise Edition 6.0
  • Microsoft Visual C++, 32-bit Professional Edition 6.0
  • Microsoft Visual C++, 32-bit Learning Edition 6.0
  • Microsoft SQL Server 7.0
This article was previously published under Q241241

SUMMARY

Visual C++ 6.0 provides the ability to create custom OLE-DB providers with the Active Template Library (ATL) Provider Templates. However, the default implementation of these providers does not work with the Data Transformation Services (DTS) provided by SQL Server 7.0.

This article describes the steps and required interfaces necessary to enable a custom ATL OLE-DB provider to work with DTS. The steps described herein concern the use of DTS through the DTS Designer and DTS Wizard. For direct programmatic access to the DTS Package and DTS DataPump, the requirements for interface support vary according to what operations are attempted and are outside the scope of this article.

MORE INFORMATION

First, the following articles should be used with an ATL Provider to ensure that the provider is working correctly before continuing:

198520 BUG: You receive an "OLE DB Provider 'atlprov' reported an error" error message when you try to use an ATL wizard-generated OLE DB Provider in Visual C++

198921 FIX: Visual C++ ATL Provider fails when used with SQL DTS

200921 OpenQuery with ATL Provider fails when set up with SQL Enterprise Manager

General Provider Problems

ODBC Drivers
Use of ODBC Drivers is provided by the OLEDB Provider for ODBC (MSDASQL), which requires that the ODBC Driver be at least ODBC version 2.5 compliant.

Non-Thread Safe Providers
DTS prompts each driver to determine if it is thread safe. When the driver reports it is thread safe, DTS attempts multiple simultaneous connections to it for parallelism. Some drivers report they are thread safe, when they are not. To force a package to run all steps on a single thread use the following Visual Basic code sample: 
Public Sub ChangeAllStepsToRunOnMainThread(oPkg As DTS.Package)
    Dim nStepCount As Integer
    For nStepCount = 1 To oPkg.Steps.Count
        oPkg.Steps(nStepCount).ExecuteInMainThread = True
    Next nStepCount
End Sub
Lack of Support for Service Components
Some drivers fail when executed as a step due to the driver's failure to properly handle service components. Change the package properties to turn off OLEDB service components.
Driver Error Messages
SQL Server 7.0 service pack 1 (SP1) addresses some issues with DTS not correctly returning error messages from the provider. It also adds some additional information in the error message on what step was being executed when the failure occurred, as most providers do not give an error message.

An error message in the wizard of "a critical error occurred" means that the driver generated an exception but DTS handled the exception.

Required Interfaces

For DTS to fully support the custom ATL OLE-DB provider the following interfaces must be implemented:

  • IAccessor: Implemented in the IAccessorImplBase and IAccessorImpl templates.
  • IColumnsInfo: Implemented in the IColumnsInfoImpl template.
  • IDBCreateSession: Implemented in the IDBCreateSessionImpl template.
  • IDBInfo: This interface is not implemented in ATL.
  • IDBInitialize: Implemented in the IDBInitializeImpl template.
  • IDBProperties: Implemented in the IDBPropertiesImpl template.
  • IOpenRowset: Implemented in the IOpenRowsetImpl template.
  • IRowset: Implemented in the IRowsetImpl template.
  • ISessionProperties: Implemented in the ISessionPropertiesImpl template.
  • IDBSchemaRowset: Implemented in the IDBSchemaRowsetImpl template. These are the schemas DTS may request:

    DBSCHEMA_PROVIDER_TYPES: This is the only one that MUST be supported.
    DBSCHEMA_TABLES
    DBSCHEMA_CATALOGS
    DBSCHEMA_PRIMARY_KEYS
    DBSCHEMA_FOREIGN_KEYS
    DBSCHEMA_INDEXES
    DBSCHEMA_TABLE_CONSTRAINTS
    DBSCHEMA_CHECK_CONSTRAINTS

Required Properties

  • DataSource: Implemented in the IGetDataSourceImpl template

Optional Interfaces

The following interfaces are optional but provide for the full experience with DTS:
  • IDBCreateCommand: Implemented in the IDBCreateCommandImpl template. Used for creating table(s)/queries and so forth.
  • ICommandText: Implemented in the ICommandTextImpl and ICommandImpl templates. Used for creating table(s)/queries and so forth.
  • ICommandPrepare: This interface is not implemented in ATL. Used for creating table(s)/queries and so forth.
  • ICommandWithParameters: This interface is not implemented in ATL. Used for Data Driven queries.
  • ITransactionJoin: This interface is not implemented in ATL. Used by DTS Package to support transactions across steps.
  • IRowsetChange: This interface is not implemented in ATL. Used by DTS to support changes to the recordset including inserts, updates or deletes. This interface is not required if the provider will only be used as a source of data.
Modification Type:MajorLast Reviewed:6/1/2005
Keywords:kbinfo KB241241 kbAudDeveloper
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