OLE DB Session Pooling Causes 100 Percent CPU Usage (MDAC 2.5) (320700)

SYMPTOMS

Microsoft COM+ continuously tries to unload OLE DB and succeeds. When OLE DB is unloaded, the session pool and its threads are freed. At the same time, new calls are being made into OLE DB, which causes the DLL to load again and the session pool to be created. The loading and unloading creates a conflict, which causes short timeouts. Additionally, you may see CPU usage go up to 100 percent for a short time (approximately 15 seconds).

CAUSE

COM+ calls the DllCanUnLoadNow function, and the OLEDB32.dll file returns true for this call. Although DllCanUnLoadNow is an inquiry, OLE DB implementation assumes that DllCanUnLoadNow is a command. As a result, OLE DB sends a "true" flag. However, OLEDB32.dll should not send "true" to this call because this call still has resources for session pooling. After COM+ receives "true" from OLEDB32.dll, COM+ unloads OLEDB32.dll. In the COM+ single-threaded apartment (STA) thread pool, this occurs very frequently. When OLEDB32.dll and the OLE DB resource pool are loaded and unloaded, CPU usage goes up to 100 percent, and you experience a delay.

RESOLUTION

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft Data Access Components service pack that contains this hotfix.

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 about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

   Date        Version       Size     File name     Platform
   -----------------------------------------------------------
   9-Apr-2002  2.52.8609.0   483,600  OLEDB32.dll   x86

MORE INFORMATION

For additional information about this problem if you are using a different version of Microsoft Data Access Components, click the article number below to view the article in the Microsoft Knowledge Base:

320698 OLE DB Session Pooling Causes 100% CPU Usage (MDAC 2.6)