HOWTO: Debug OLE DB Providers That Are Called From SQL Server 7.0

ID: Q222123

The information in this article applies to:

Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0

SUMMARY

This article provides tips for debugging OLE DB Providers which are called from SQL Server version 7.0. Moreover, SQL Server 7.0 can perform distributed queries by using the OPENROWSET and OPENQUERY Transact SQL functions.

MORE INFORMATION

Specify that the OLE DB Provider is to be Loaded in the SQL Server Process Space.

By default, an OLE DB Provider is invoked by SQL Server as an out-of-process component. This is done by using proxy/stub code in Msdaps.dll which is provided with the OLE DB core components. The OLE DB provider is hosted by using Dllhost.exe and is the surrogate process for the OLE DB Provider. Because it is difficult to attach to the Dllhost.exe process with the Visual C++ debugger, it is recommended that you mark the provider as in-process for debugging purposes. You can then attach the debugger to the SQL Server process Sqlservr.exe.
To mark a provider as in-process, use one of the following two processes:

Create a linked server in SQL Server 7.0 which specifies the provider. In the SQL Enterprise Manager, click Properties for the new linked server, choose Options, and then select Allow InProcess.

Add the provider ProgID to a key in the register at: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Providers and add a DWORD value under that key which is AllowInProcess with a value of 1.

NOTE: Once you have marked the provider as in-process, you can then attach to SQL Server and more easily debug the provider.

Attach the Debugger to the SQL Server Process

This can be done by going to Build. Click Start. Select Debug and click Attach to Process in the Visual C++ development environment. When the process list displays, select Show System Processes and you should see SQLSERVR appear in the list. This is the SQL Server process. Select it and the debugger will attach to the process. Go to Project then click Settings and select the Debug tab and add your OLE DB Provider DLL to the list of additional DLLs. This causes the debug information for your DLL to be loaded so breakpoints can be set in your OLE DB Provider source code.

Debugging Providers which are Invoked Out-of-Process

Occasionally, a problem will occur only when an OLE DB Provider is invoked out-of-process. By default, SQL server invokes OLE DB Providers out-of-process. This can be changed by using the steps described earlier in this article. However, if you must debug a problem which only occurs when the provider is out-of-process, you need to have a way to attach the debugger to the component. Following are a couple of ways to accomplish this:

Put a Sleep() in the constructor of the datasource object of the provider so that you have time to attach the debugger to the Dllhost.exe process which is the surrogate for the provider.

Add code to the provider so the debugger will attach automatically. Insert the following code into the FinalConstruct() for the datasource object:


HRESULT FinalConstruct()
{
   if (!IsDebuggerPresent())
   {
     char szDebuggerCmd[100];
     wsprintf(szDebuggerCmd, "C:\\Program Files\\Microsoft Visual Studio\\Common\\MSDev98\\Bin\\MSDEV -p %ld", (long)GetCurrentProcessId());
     PROCESS_INFORMATION pi;
     STARTUPINFO si;
     ZeroMemory(&si, sizeof(si));
     si.cb = sizeof(si);
     si.lpDesktop = "Winsta0\\Default";
     CreateProcess(NULL, szDebuggerCmd, NULL, NULL, TRUE, 0, NULL, NULL,  &si, &pi); 
     Sleep(5000);
     _asm int 3
   }

   return FInit();
}

Enable OLE DB Tracing in Query Analyzer

You can have OLE DB trace information returned in Query Analyzer by typing the command: DBCC traceon(7300). After executing a distributed query, if the provider returned an error, diagnostic information will be displayed in the results window.

Enable OLE DB Tracing in SQL Server Profiler

The SQL Server Profiler application also provides diagnostic traces for OLE DB calls. To get information about OLE DB errors and warnings, do the following:

Start the SQL Server 7.0 Profiler application.

Go to Tools and click Options. Click the General tab and select All event classes.

Open a trace file by going to File and click New or go to File and click Open, and then go to File and click Properties.

A dialog entitled Trace Properties will be displayed. Click the Events tab.

Select Error and Warning events and select the OLEDB errors event.

If your OLE DB provider returns an error to SQL Server, the trace displays the OLE DB call that failed and the return value.

REFERENCES

For additional information, see the Support WebCast at the following location:

http://support.microsoft.com/servicedesks/webcasts/wc102699/WC102699.asp

Additional query words:

Keywords : kbDatabase kbOLEDB kbProvider kbSQLServ kbATL300 kbGrpVCDB
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbhowto