FIX: Parallel Query on Four CPUs Using NLS Is Slower Than Two CPUs

Parallel query performance on a computer with four CPUs is poorer than on a computer with two CPUs if you are using the National Language Support (NLS) sort order with the double-byte character set (DBCS).

You may encounter this problem if all of the following conditions are true:

• You are using the NLS sort order with DBCS.
• The query processor chooses the Parallelism physical operator.
• The table has a column of character data type that is used by the Parallelism physical operator.

To work around this problem, do one of the following:

• Use the binary sort order.
  
  -or-
• Restrict the number of threads in parallel plan execution, by using the "max degree of parallelism" option or MAXDOP query hint.

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: For more information, contact your primary support provider.