Microsoft KB Archive/835864

= FIX: Intermittent query slowdowns and corresponding high CPU utilization =

Article ID: 835864

Article Last Modified on 11/2/2007

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APPLIES TO


 * Microsoft SQL Server 2000 Developer Edition
 * Microsoft SQL Server 2000 Standard Edition
 * Microsoft SQL Server 2000 Enterprise Edition
 * Microsoft SQL Server 2000 Personal Edition
 * Microsoft SQL Server 2000 Enterprise Edition
 * Microsoft SQL Server 2000 Workgroup Edition
 * Microsoft SQL Server 2000 Desktop Engine (Windows)
 * Microsoft SQL Server 2000 Developer Edition
 * Microsoft SQL Server 2000 Enterprise Edition 64-bit

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Bug #: 470933 (SHILOH_BUGS)



Microsoft SQL Server 2000 fixes are distributed as one downloadable file. Because the fixes are cumulative, each new release contains all the hotfixes and all the security fixes that were included in the previous SQL Server 2000 fix release.



SYMPTOMS
You have a workload that is running on a multiprocessor computer that forces SQL Server to perform many memory allocation operations and memory free operations each second (several hundred small batches that require compilation each second, for example). You may notice that a query that typically runs in a certain time takes longer to complete, although the query processes the same amount of data, uses the same query plan, and performs the same amount of I/O. The only noticeable difference is an increase in the CPU time and the elapsed time that it takes to run the query. In extreme cases, you may find that simple queries (such as SET ROWCOUNT 0) might take several hundred milliseconds to run and several hundred milliseconds of CPU time.



Service pack information
To resolve this problem, obtain the latest service pack for Microsoft SQL Server 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

290211 How to obtain the latest SQL Server 2000 service pack

Hotfix information
The English version of this hotfix 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         Time   Version            Size    File name 31-May-2003 18:45  2000.80.818.0      78,400  Console.exe 28-Oct-2003 04:21  2000.80.873.0     315,968  Custtask.dll 02-Oct-2003 20:59  2000.80.867.0      33,340  Dbmslpcn.dll 25-Apr-2003 02:12                    786,432  Distmdl.ldf 25-Apr-2003 02:12                  2,359,296  Distmdl.mdf 30-Jan-2003 01:55                        180  Drop_repl_hotfix.sql 12-Sep-2003 03:26  2000.80.859.0   1,905,216  Dtspkg.dll 26-Aug-2003 20:16  2000.80.854.0     528,960  Dtspump.dll 23-Jun-2003 22:40  2000.80.837.0   1,557,052  Dtsui.dll 23-Jun-2003 22:40  2000.80.837.0     639,552  Dtswiz.dll 24-Apr-2003 02:51                    747,927  Instdist.sql 10-Oct-2003 18:52                    745,961  Instmsdb.sql 03-May-2003 01:56                      1,581  Inst_repl_hotfix.sql 08-Feb-2003 06:40  2000.80.765.0      90,692  Msgprox.dll 01-Apr-2003 02:07                      1,873  Odsole.sql 05-Apr-2003 01:46  2000.80.800.0      62,024  Odsole70.dll 07-May-2003 20:41  2000.80.819.0      25,144  Opends60.dll 02-Apr-2003 21:48  2000.80.796.0      57,904  Osql.exe 02-Apr-2003 23:15  2000.80.797.0     279,104  Pfutil80.dll 04-Aug-2003 18:17                    550,780  Procsyst.sql 12-Sep-2003 00:37                     12,305  Qfe469315.sql 22-May-2003 22:57                     19,195  Qfe469571.sql 20-Jan-2004 00:45                  1,090,380  Replmerg.sql 06-Sep-2003 07:18  2000.80.858.0     221,768  Replprov.dll 16-Jan-2004 01:24  2000.80.908.0     307,784  Replrec.dll 16-Jan-2004 01:13  2000.80.908.0     159,813  Replres.rll 06-Sep-2003 00:00                  1,087,150  Replsys.sql 13-Aug-2003 16:28                    986,603  Repltran.sql 02-Jan-2004 19:42  2000.80.904.0     287,304  Rinitcom.dll 22-Oct-2003 00:08  2000.80.871.0      57,916  Semnt.dll 29-Jul-2003 20:13  2000.80.819.0     492,096  Semobj.dll 31-May-2003 18:27  2000.80.818.0     172,032  Semobj.rll 02-Jan-2004 19:42  2000.80.904.0      53,832  Snapshot.exe 09-Dec-2003 20:07                    117,834  Sp3_serv_uni.sql 16-Jan-2004 01:23  2000.80.908.0      28,672  Sqlagent.dll 16-Jan-2004 01:24  2000.80.908.0     311,872  Sqlagent.exe 07-Jan-2004 22:38  2000.80.905.0     126,976  Sqlakw32.dll 01-Jun-2003 01:01  2000.80.818.0   4,215,360  Sqldmo.dll 07-Apr-2003 17:44                     25,172  Sqldumper.exe 19-Mar-2003 18:20  2000.80.789.0      28,672  Sqlevn70.rll 27-Sep-2003 04:42  2000.80.865.0     180,792  Sqlmap70.dll 03-Sep-2003 02:56  2000.80.857.0     188,992  Sqlmmc.dll 02-Sep-2003 23:03  2000.80.857.0     479,232  Sqlmmc.rll 22-Oct-2003 00:08  2000.80.871.0     401,984  Sqlqry.dll 08-Feb-2003 06:40  2000.80.765.0      57,920  Sqlrepss.dll 24-Jan-2004 01:59  2000.80.910.0   7,610,449  Sqlservr.exe 25-Jul-2003 21:44  2000.80.845.0     590,396  Sqlsort.dll 08-Feb-2003 06:40  2000.80.765.0      45,644  Sqlvdi.dll 24-Jan-2004 01:59  2000.80.910.0     106,588  Sqsrvres.dll 02-Oct-2003 20:59  2000.80.867.0      33,340  Ssmslpcn.dll 01-Jun-2003 01:01  2000.80.818.0      82,492  Ssnetlib.dll 01-Jun-2003 01:01  2000.80.818.0      25,148  Ssnmpn70.dll 28-Oct-2003 04:21  2000.80.873.0     123,456  Stardds.dll 01-Jun-2003 01:01  2000.80.818.0     158,240  Svrnetcn.dll 31-May-2003 18:59  2000.80.818.0      76,416  Svrnetcn.exe 30-Apr-2003 23:52  2000.80.816.0      45,132  Ums.dll 02-Jul-2003 00:19  2000.80.834.0      98,816  Xpweb70.dll Note Because of file dependencies, the most recent hotfix or feature that contains these files may also contain additional files.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section of this article.

This problem was first corrected in Microsoft SQL Server 2000 Service Pack 4.



MORE INFORMATION
For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the Standard Terminology That Is Used to Describe Microsoft Software Updates

Most memory allocation requests in SQL Server are handled by allocating a page from the buffer pool. SQL Server maintains counters to track how many pages have been stolen from the buffer pool to be use as a generic memory buffer instead of a buffer for a database page. The DBCC MEMORYSTATUS command makes part of this information available and is automatically logged in the error log in certain out-of-memory conditions. These numbers are also used to trigger other events in the server, such as the lazywriter process. For additional information about these counters and stolen memory, click the following article number to view the article in the Microsoft Knowledge Base:

271624 INF: Using DBCC MEMORYSTATUS to monitor SQL Server memory usage

On multiprocessor computers, access to these counter values must be serialized. SQL Server serializes the counter values by using a spinlock. With a spinlock, the thread that wants to acquire the spinlock tries to acquire the lock. If the lock is not available, the thread spins in a loop, periodically rechecking the availability of the resource. If the operation that occurs inside the spinlock protection has a very short duration, such as incrementing or decrementing a counter, using a spinlock can be much faster than using a kernel synchronization object and then switching from user mode to kernel mode and back. However, if the spinlock becomes highly contended, a thread may spend more time spinning and trying to acquire the lock than it does performing useful work. Because of this, spinlocks are not a good choice for protecting a heavily-contended data structure.

This hotfix uses a different synchronization mechanism to maintain these counter values. It requires a substantial amount of contention to cause any noticeable delay or increase in CPU time. Typically, you must have a server with 8 or more processors (so that 8 threads are running at the same time) to be able to process a workload that can generate this much contention. This much contention may be more likely to occur if hyperthreading is enabled because it effectively doubles the number of SQL threads that can be running.

Keywords: kbbug kbfix kbqfe kbsqlserv2000presp4fix kbhotfixserver KB835864

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