Microsoft KB Archive/263695

= BUG: UPDATE Statement with SELECT DISTINCT Subquery with Parallelism Enabled May Cause Access Violation =

Article ID: 263695

Article Last Modified on 10/3/2003

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APPLIES TO


 * Microsoft SQL Server 7.0 Service Pack 2

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This article was previously published under Q263695



BUG #: 57948 (SQLBUG_70)



SYMPTOMS
When you run an UPDATE statement with a SELECT DISTINCT subquery, which involves a merge join, an access violation (AV) may occur.

This only happens on a multi-processor computer that has the Max Degree of Parallelism set to 0 (ON).



WORKAROUND
Set the Max Degree of Parallelism option to 1 (OFF) to prevent the access violation. You can set this value either at the:  Server level by using the Sp_configure option or from Enterprise Manager.

For example:

  From Query Analyzer, running the following code to turn off Max degree of Parallelism: sp_configure 'max degree of parallelism', 1 go reconfigure with override go  From Enterprise Manager, right-click the server name, click Properties, and then click the Processor tab. Under the Parallelism category, select the option Use # of Processor(s) and specify 1 as the value.

-or

  Query level by using the hint &quot;OPTION (MAXDOP 1)&quot;.

For example: USE PUBS GO SELECT * FROM authors OPTION (MAXDOP 1) GO The code turns the Max Degree of Parallelism off at the query level without affecting any other queries or operations. 

<div class="status_section">

STATUS
Microsoft has confirmed this to be a problem in SQL Server 7.0.

Keywords: kbbug kbpending KB263695

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