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SQL Server may experience access violations when canceling a DB2 query

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This article helps you resolve the problem that occurs when a user cancels a linked server query against an IBM DB2 database.

Original product version:   Host Integration Server 2010
Original KB number:   2761993

Symptoms

Consider the following scenario:

  • You have a Linked Server that connects to an IBM DB2 database using the OLE DB Provider for DB2.

  • The DB2 connection string includes the Rowset Cache Size parameter with a non-zero value (for example, Rowset Cache Size=100).

If a user attempts to cancel a query that is currently executing via the Linked Server to the IBM DB2 database, the SQL Server process may report an access violation and create a dump file.

Cause

The problem occurs because of a synchronization problem in the Microsoft OLE DB Provider for DB2 when canceling a running query when the Rowset Cache Size feature is enabled.

Resolution

Change the DB2 connection string in the Linked Server to include the parameter: Rowset Cache Size=0

The SQL Server process needs to be restarted after making this change to make sure the new connection string is loaded by the DB2 provider.

More information

The RowSet Cache Size parameter instructs the DB2 data provider to pre-fetch rows from DB2 while concurrently processing and returning rows to the data consumer. This feature may improve performance in bulk read-only operations on multi-processor or multi-core computers. The default value for this property is 0 (Rowset Cache Size=0), which indicates that the optional pre-fetch feature is "off".

It is not recommended to enable this parameter (use a non-zero value) for scenarios other than bulk-read operations that require a high level of performance.