Microsoft KB Archive/870972

= FIX: The performance of a DML operation that fires a trigger may decrease when the trigger execution plan recompiles repeatedly =

Article ID: 870972

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 #: 470083 (SQL Server 8.0)



Article contents
 Summary Symptoms Resolution 

Hotfix information

 

Prerequisites

 

Restart information

 

Hotfix file information

</li> Status</li> More Information</li> References</li></ul>

<div class="summary_section">

SUMMARY
This article describes the following about this hotfix release:
 * The issues that are fixed by this hotfix package.
 * The prerequisites for installing the hotfix package.
 * Whether you must restart your computer after you install the hotfix package.
 * Whether the hotfix package is replaced by any other hotfix package.
 * Whether you must make any registry changes.
 * The files that are contained in the hotfix package.

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<div class="symptoms_section">

SYMPTOMS
When you run a data manipulation language (DML) statement such as an UPDATE, INSERT, or DELETE statement that fires a trigger, the Microsoft SQL Server program recompiles the trigger execution plan to improve the performance of the trigger execution. However, the repeated recompilation of the trigger execution plan may decrease the performance of the trigger execution.

The repeated recompilation of the trigger execution plan may occur when the following conditions are true:
 * You run the DML statement multiple times.
 * The number of rows that are affected by the DML statement differs every time that the DML statement is run.

For a list of previous hotfixes, see the &quot;Microsoft SQL Server 2000 post-Service Pack 3 or Microsoft SQL Server 2000 post-Service Pack 3a hotfixes&quot; section in the following Microsoft Knowledge Base article:

290211 How to obtain the most recent SQL Server 2000 service pack

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<div class="resolution_section">

Service pack information
To resolve this problem, obtain the latest service pack for Microsoft SQL Server 2000. For more 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

Prerequisites
This hotfix requires Microsoft SQL Server 2000 Service Pack 3 (SP3). For additional information about how to obtain SQL Server 2000 Service Pack 3, click the following article number to view the article in the Microsoft Knowledge Base:

290211 How to obtain the most recent SQL Server 2000 service pack

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Restart information
You do not have to restart your computer after you apply this hotfix.

Note After you apply this hotfix, you must restart your SQL Server 2000 program that is running on your computer.

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Hotfix file information
This hotfix contains only those files that are required to correct the issues that this article lists. This hotfix may not contain all the files that you must have to fully update a product to the latest build.

The English version of this hotfix has the file attributes (or later file attributes) 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. <pre class="fixed_text">   Date         Time   Version       Size       File name --  18-Jun-2004  14:14  2000.80.954.0    664,128  Autoplt.dll 18-Jun-2004 14:14  2000.80.954.0     78,400  Console.exe 18-Jun-2004 14:14  2000.80.954.0    315,968  Custtask.dll 18-Jun-2004 14:14  2000.80.954.0     33,340  Dbmslpcn.dll 08-Apr-2004 09:12                   786,432  Distmdl.ldf 08-Apr-2004 09:12                 2,359,296  Distmdl.mdf 10-Oct-2003 06:18                       180  Drop_repl_hotfix.sql 18-Jun-2004 14:14  2000.80.954.0  1,905,216  Dtspkg.dll 18-Jun-2004 14:14  2000.80.954.0    528,960  Dtspump.dll 18-Jun-2004 14:14  2000.80.954.0  1,557,052  Dtsui.dll 18-Jun-2004 14:14  2000.80.954.0    639,552  Dtswiz.dll 10-Oct-2003 06:18                   747,927  Instdist.sql 10-Oct-2003 06:18                     1,581  Inst_repl_hotfix.sql 18-Jun-2004 14:14  2000.80.954.0    352,828  Isqlw.exe 18-Jun-2004 14:14  2000.80.954.0     82,492  Itwiz.exe 18-Jun-2004 14:14  2000.80.954.0     90,692  Msgprox.dll 19-May-2004 11:13  8.11.40209.0     209,408  Mssdi98.dll 18-Jun-2004 14:14  2000.80.954.0     62,024  Odsole70.dll 18-Jun-2004 14:15  2000.80.954.0     25,144  Opends60.dll 18-Jun-2004 14:14  2000.80.954.0     57,904  Osql.exe 18-Jun-2004 14:14  2000.80.954.0    279,104  Pfutil80.dll 10-Oct-2003 06:07                   550,780  Procsyst.sql 08-Apr-2004 09:12                    12,305  Qfe469315.sql 08-Apr-2004 09:12                    19,195  Qfe469571.sql 17-Jun-2004 02:42                 1,105,167  Replmerg.sql 18-Jun-2004 14:14  2000.80.954.0    221,768  Replprov.dll 18-Jun-2004 14:14  2000.80.954.0    307,784  Replrec.dll 16-Jun-2004 14:07  2000.80.954.0    159,813  Replres.rll 10-Oct-2003 06:18                 1,087,150  Replsys.sql 10-Oct-2003 06:18                   986,603  Repltran.sql 18-Jun-2004 14:14  2000.80.954.0    287,304  Rinitcom.dll 18-Jun-2004 14:14  2000.80.954.0     78,416  Sdiclnt.dll 18-Jun-2004 14:14  2000.80.954.0     66,112  Semmap.dll 18-Jun-2004 14:14  2000.80.954.0     57,916  Semnt.dll 18-Jun-2004 14:14  2000.80.954.0    492,096  Semobj.dll 16-Jun-2004 14:44  2000.80.954.0    172,032  Semobj.rll 18-Jun-2004 14:14  2000.80.954.0     53,832  Snapshot.exe 11-Mar-2004 14:40                   117,834  Sp3_serv_uni.sql 18-Jun-2004 14:13  2000.80.954.0     28,672  Sqlagent.dll 18-Jun-2004 14:14  2000.80.954.0    311,872  Sqlagent.exe 18-Jun-2004 14:13  2000.80.954.0    168,001  Sqlakw32.dll 18-Jun-2004 14:14  2000.80.954.0     33,344  Sqlctr80.dll 18-Jun-2004 14:14  2000.80.954.0  4,215,360  Sqldmo.dll 18-Jun-2004 14:14                    25,172  Sqldumper.exe 16-Jun-2004 13:54  2000.80.954.0     28,672  Sqlevn70.rll 18-Jun-2004 14:14  2000.80.954.0    180,792  Sqlmap70.dll 18-Jun-2004 14:14  2000.80.954.0    188,992  Sqlmmc.dll 16-Jun-2004 14:52  2000.80.954.0    479,232  Sqlmmc.rll 18-Jun-2004 14:14  2000.80.954.0    401,984  Sqlqry.dll 18-Jun-2004 14:14  2000.80.954.0     57,920  Sqlrepss.dll 18-Jun-2004 14:14  2000.80.954.0  7,581,777  Sqlservr.exe 18-Jun-2004 14:14  2000.80.954.0    590,396  Sqlsort.dll 18-Jun-2004 14:14  2000.80.954.0     45,644  Sqlvdi.dll 18-Jun-2004 14:14  2000.80.954.0    106,588  Sqsrvres.dll 18-Jun-2004 14:14  2000.80.954.0     33,340  Ssmslpcn.dll 18-Jun-2004 14:14  2000.80.954.0     82,492  Ssnetlib.dll 18-Jun-2004 14:14  2000.80.954.0     25,148  Ssnmpn70.dll 18-Jun-2004 14:14  2000.80.954.0    123,456  Stardds.dll 18-Jun-2004 14:14  2000.80.954.0    158,240  Svrnetcn.dll 18-Jun-2004 14:14  2000.80.954.0     76,416  Svrnetcn.exe 18-Jun-2004 14:14  2000.80.954.0     49,228  Ums.dll 18-Jun-2004 14:14  2000.80.954.0     98,872  Xpweb70.dll Note Because of file dependencies, the most recent hotfix that contains these files may also contain additional files.back to the top

<div class="status_section">

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

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

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<div class="moreinformation_section">

MORE INFORMATION
This hotfix update improves the thresholds at which the execution plan of a trigger is recompiled. For thresholds improvement to take effect, you must enable SQL Server trace flag 9055 after you install this hotfix. To enable trace flag 9055 for an instance of SQL Server, use one of the following methods: <ul>  Run the following Transact-SQL statement in SQL Query Analyzer on the instance of SQL Server: DBCC TRACEON (9055, -1) </li> Add -T9055 to the SQL Server startup parameters.</li></ul>

Steps to reproduce the behavior
To reproduce a scenario that causes a trigger execution plan recompilation, follow these steps: <ol> Start SQL Query Analyzer, and then connect to an instance of SQL Server 2000.</li>  Create a table and an update trigger on the table. Name the table as cache_test and name the update trigger as cache_test_update. To do this, run the following Transact-SQL statements: use pubs go set nocount on go if exists (select 1 from sysobjects where id = object_id('dbo.cache_test')) drop table dbo.cache_test go create table dbo.cache_test ( id int not null, descr varchar(30) not null, rowcreateddt datetime not null default getdate, rowcreatedby varchar(30) not null default right(system_user,30), testcolumn varchar(30) null, primary key (id) ) go

create trigger dbo.cache_test_update on dbo.cache_test for update as if exists ( select 1 from inserted where id = 98654 ) print 'test' return go </li>  Insert some records in the cache_test table, and then remove all elements from the procedure cache. To do this, run the following Transact-SQL statements: insert into cache_test (id, descr, testcolumn) select 1,'Descr 1','Test 1' insert into cache_test (id, descr, testcolumn) select 2,'Descr 2','Test 2' insert into cache_test (id, descr, testcolumn) select 3,'Descr 3','Test 3' insert into cache_test (id, descr, testcolumn) select 4,'Descr 4','Test 4' insert into cache_test (id, descr, testcolumn) select 5,'Descr 5','Test 5' insert into cache_test (id, descr, testcolumn) select 6,'Descr 6','Test 6' insert into cache_test (id, descr, testcolumn) select 7,'Descr 7','Test 7' insert into cache_test (id, descr, testcolumn) select 8,'Descr 8','Test 8' insert into cache_test (id, descr, testcolumn) select 9,'Descr 9','Test 9' insert into cache_test (id, descr, testcolumn) select 10,'Descr 10','Test 10' go

dbcc freeproccache </li>  Update a single row in the table cache_test, and then see the plan for this single row update that is in the cache. To do this, run the following Transact-SQL statements: update cache_test set testcolumn = 'testing '+cast(id as varchar) where id between 1 and 1 go

select SetOpts,UseCounts,* from master..SyscacheObjects where ObjId=Object_ID('cache_test_update') order by SetOpts, CacheObjType go You notice an output that is similar to the following:

<pre class="fixed_text">SetOpts UseCounts bucketid cacheobjtype    objtype  objid      dbid dbidexec uid refcounts usecounts pagesused lasttime maxexectime avgexectime lastreads lastwrites setopts langid dateformat status sqlbytes sql 5371   1     10394    Compiled Plan    Trigger  1029578706 5    5        1   2     1         1         0    0       0           0     0          5371    0      1          0   34  cache_test_update 5371   1     10394    Executable Plan  Trigger  1029578706 5    5        1   1     1         1         0    0       0           0     0          5371    0      1          0   34  cache_test_update </li>  Update four rows in the cache_test table, and then see the plan for this multiple-row update that is in the cache. To do this, run the following Transact-SQL statements: update cache_test set testcolumn = 'testing '+cast(id as varchar) where id between 1 and 4 go

select SetOpts,UseCounts,* from master..SyscacheObjects where ObjId=Object_ID('cache_test_update') order by SetOpts, CacheObjType go You will notice an output that is similar to the following:

<pre class="fixed_text">SetOpts UseCounts bucketid cacheobjtype    objtype  objid      dbid dbidexec uid refcounts usecounts pagesused lasttime maxexectime avgexectime lastreads lastwrites setopts langid dateformat status sqlbytes sql 4347   1     10394    Compiled Plan    Trigger  1029578706 5    5        1   2     1         1         0    0       0           0     0          4347    0      1          0   34  cache_test_update 4347   1     10394    Executable Plan  Trigger  1029578706 5    5        1   1     1         1         0    0       0           0     0          4347    0      1          0   34  cache_test_update 5371   1     10394    Compiled Plan    Trigger  1029578706 5    5        1   2     1         1         0    0       0           0     0          5371    0      1          0   34  cache_test_update 5371   1     10394    Executable Plan  Trigger  1029578706 5    5        1   1     1         1     0    0       0           0     0          5371    0      1          0   34  cache_test_update </li>  Update five rows) in the cache_test table, and then see the plan for this multiple-row update that is in the cache. To do this, run the following Transact-SQL statements: update cache_test set testcolumn = 'testing '+cast(id as varchar) where id between 1 and 5 go

select SetOpts,UseCounts,* from master..SyscacheObjects where ObjId=Object_ID('cache_test_update') order by SetOpts, CacheObjType go You notice an output that is similar to the following:

<pre class="fixed_text">SetOpts UseCounts bucketid cacheobjtype    objtype  objid      dbid dbidexec uid refcounts usecounts pagesused lasttime maxexectime avgexectime lastreads lastwrites setopts langid dateformat status sqlbytes sql 4347   1     10394    Compiled Plan    Trigger  1029578706 5    5        1   2     1         1         0    0       0           0     0          4347    0      1          0   34  cache_test_update 4347   2     10394    Executable Plan  Trigger  1029578706 5    5        1   1     2         1         0    0       0           0     0          4347    0      1          0   34  cache_test_update

If you compare this output with the output in step 5, you may notice the following conditions that could lead to the decrease in performance of the trigger execution: <ul> The execution plan that corresponds to the multiple row update in the output of step 5 is deleted. This behavior occurs because the execution plan that corresponds to the multiple row update is recompiled to create a new execution plan.</li> Even though the execution plan appears to have been recompiled, the usecounts column indicates that the Executable Plan has been used two times. That is not correct.</li> Additionally, the execution plan that corresponds to the single row update has been deleted from the cache.</li></ul> </li></ol>

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<div class="references_section">