BUG: Different MTS Transaction Contexts Cause Increase in Connections

ID: Q224320

The information in this article applies to:

SYMPTOMS

If you are using ADO within components that are running under Microsoft Transaction Server (MTS), and the components have different transactional contexts, additional connections may be opened to database server.

Connections opened in a package with multiple components, some marked transactional, some not, will be stored in the OLE DB Session Pool. However, under some circumstances, connections opened in a component marked as "Requires a Transaction," or "Requires a New Transaction," will have their connections stored in the pool as non-transactional. These connections will not be reused by the application, and will be dropped after the normal 60-second timeout. However, under high-activity conditions, this can cause the database server to run out of available connections.

The easiest way to see this behavior is for a package with three components, each of which just opens a Connection via ADO (or OLE DB), two of which are marked as "Supports Transactions," the third marked as "Requires a Transaction."

The problem does not appear to happen if the transactional contexts are evenly divided: for example, if there is one component set to "Supports Transactions" and one component set to "Requires a Transaction." The problem occurs when there is an imbalance in the contexts, such as having two set to "Supports Transactions" and one set to "Requires a Transaction." This is not fully tested, but may offer an additional workaround.


CAUSE

The OLE DB Service Component (msdasc.dll) is receiving incorrect information from the MTS Dispenser Manager (mtxdm.dll) as to the condition of the current transactional context. This is causing the OLE DB Service Components to store connections opened in a transactional context in the pool as opened with a non-transactional context. OLE DB Session Pooling will never return a non-transactional connection to a consumer that is marked as transactional. Because of this, OLE DB will believe that there are no connections that currently match the the transactional requirements, and a new connection is generated.


RESOLUTION

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Microsoft Data Access Components (MDAC) Service Pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

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

   Date      Time   Version      Size    File name   Platform
   ---------------------------------------------------------
   03/26/99  02:55p 02.10.3926.0   5,392 msdadc.dll     x86
   03/26/99  02:56p 02.10.3926.0   5,392 msdaenum.dll   x86
   03/26/99  02:56p 02.10.3926.0   5,392 msdaer.dll     x86
   03/26/99  02:56p 02.10.3926.0   5,392 msdasc.dll     x86
   03/26/99  02:56p 02.10.3926.0 366,352 oledb32.dll    x86
   03/26/99  02:56p 02.10.3926.0  40,720 oledb32r.dll   x86
   03/26/99  02:56p 02.10.3926.0   5,392 oledb32x.dll   x86


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



NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee.

For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base:
Q154871 Determining If You Are Eligible for No-Charge Technical Support


WORKAROUND

In addition to the hotfix described in this article, there are two other possible workarounds for this problem:


STATUS

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

Additional query words: connection stacking reused session pooling MTS components different transaction context timeout 


Keywords          : kbADO kbADO200fix kbADO210fix kbMDAC kbOLEDB kbOLEDB200fix kbOLEDB210fix kbGrpVBDB 
Version           : WINDOWS:2.0,2.1,2.5
Platform          : WINDOWS 
Issue type        : kbbug

Last Reviewed: July 2, 1999