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FIX: OPTION (MAXDOP 1) Hint May Not Turn Off Parallel Query

This article was previously published under Q266372
BUG #: 58092 (SQLBUG_70)
SYMPTOMS
A complex UPDATE statement using the OPTION (MAXDOP 1) hint on multiprocessor computers may not turn off parallel query plan.
WORKAROUND
To turn off parallelism, do one of the following:
  • Run the following code:
    sp_configure 'max degree of parallelism', 1goreconfigure with override					
    -or-

  • Increase 'cost threshold for parallelism' in sp_configure to reduce the chance of a parallel query plan being chosen for the query. One would have to test and find the minimum value for this setting on your computer to avoid a parallel plan for the query because it is related to both the query and the data in the tables involved in the query.
STATUS
Microsoft has confirmed this to be a problem in SQL Server 7.0. This problem has been corrected in U.S. Service Pack 3 for Microsoft SQL Server 7.0. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
274799 INF: How to Obtain Service Pack 3 for Microsoft SQL Server 7.0 and Microsoft Data Engine (MSDE) 1.0
For more information, contact your primary support provider.
MORE INFORMATION
The following is an example of the complex UPDATE query reported in this bug:
UPDATE  tab_x SET   c1 = tab0.a,  c2 = tab1.a,  c3 = tab2.a,  c4 = tab3.a,  c5 = tab4.a,  c6 = tab5.a,  c7 = tab6.a,  c8 = tab7.aFROM   tab_y INNER JOIN tab_x ON tab_y.b1 = tab_x.c9   LEFT OUTER JOIN tab7 ON tab_y.b2 = tab7.b2   LEFT OUTER JOIN tab6 ON tab_y.b3 = tab6.b2  LEFT OUTER JOIN tab5 ON tab_y.b4 = tab5.b2   LEFT OUTER JOIN tab4 ON tab_y.b5 = tab4.b2  LEFT OUTER JOIN tab3 ON tab_y.b6 = tab3.b2   LEFT OUTER JOIN tab2 ON tab_y.b7 = tab2.b2   LEFT OUTER JOIN tab1 ON tab_y.b8 = tab1.b2   LEFT OUTER JOIN tab0 ON tab_y.b9 = tab0.b2				
Properties

Article ID: 266372 - Last Review: 03/14/2006 10:30:04 - Revision: 2.1

  • Microsoft SQL Server 7.0 Standard Edition
  • kbbug kbfix KB266372
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