Running a certain sequence of commands involving explicit transactions and parameters in an application program using the SQLOLEDB Provider incorrectly leaves an uncommitted transaction open. This can cause severe blocking and other problems.

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Although the SET option 'implicit_transactions' is set to OFF, the SQLOLEDB Provider is opening an implicit transaction.

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MDAC 2.6

To resolve this problem, obtain the latest service pack for Microsoft Data Access Components 2.6. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

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Hotfix

IMPORTANT: Microsoft Data Access Components version 2.6 must be installed before applying this hotfix.

The English version of this fix should have the following file attributes or later:

   Date       Time     Version     Size      File name      Platform
   -----------------------------------------------------------------
   11/22/00   8:43pm   8.00.0225   491,584   Sqloledb.dll   Intel
   11/22/00   8:43pm   8.00.0225    61,440   Sqloledb.rll   Intel
				

NOTE: Due to file dependencies, the most recent hotfix or feature that contains the above files may also contain additional files.

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To work around this problem, do either of the following:

•	Use the OLEDB Provider for ODBC rather than the SQLOLEDB Provider. -or-
•	Put additional transactions around the code that creates the problem.

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Microsoft has confirmed this to be a problem in the Microsoft OLE DB Provider for SQL Server that is included in Microsoft Data Access Components (MDAC) versions 2.1, 2.5, and 2.6.

MDAC 2.6

This problem was first corrected in Microsoft Data Access Components 2.6 Service Pack 1.

MDAC 2.5

This problem was first corrected in the version of Sqlredis.exe that is included with Microsoft SQL Server 7.0 Service Pack 4.

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Through tracing the application, you can see in SQL Server Profiler that the SQLOLEDB Provider is sending the following statements to SQL Server:

SET FMTONLY ON select ... SET FMTONLY OFF
set implicit_transactions off SET NO_BROWSETABLE OFF
				

This causes an 'implicit_transaction' being already opened.

When using the OLEDB Provider for ODBC and the SQL Server driver instead, the exact same Visual Basic/ADO code sends the following statements to SQL Server:

set implicit_transactions off SET NO_BROWSETABLE OFF
SET FMTONLY ON select  ... SET FMTONLY OFF
				

Thus the FMTONLY SELECT opens an implicit transaction with SQLOLEDB. However, because the application never opened this transaction, the application will normally never close it. This transaction will only be closed upon the next explicit transaction.

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