FIX: You may receive a BPool::Map warning when you create or rebuild indexes by using the awe enabled configuration option (838459)

SYMPTOMS

When you run a CREATE INDEX statement or a DBCC DBREINDEX statement on a computer that is running SQL Server, and the awe enabled configuration option is set to 1, the following BPool::Map warning and the DBCC MEMORYSTATUS statement may be written to the SQL Server error log: 2004-02-26 07:36:21.10 spid52 BPool::Map: no remappable address found.
2004-02-26 07:36:21.24 spid52 Buffer Distribution: Stolen=149242 Free=389930 Procedures=2 Inram=0 Dirty=92791 Kept=0 I/O=0, Latched=10, Other=264025
2004-02-26 07:36:21.24 spid52 Buffer Counts: Commited=896000 Target=896000 Hashed=356826 InternalReservation=104 ExternalReservation=280 Min Free=224
2004-02-26 07:36:21.24 spid52 Procedure Cache: TotalProcs=1 TotalPages=2 InUsePages=2
2004-02-26 07:36:21.24 spid52 Dynamic Memory Manager: Stolen=921 OS Reserved=1600 OS Committed=1559 OS In Use=1557 Query Plan=13 Optimizer=0 General=1712 Utilities=23 Connection=58
2004-02-26 07:36:21.24 spid52 Global Memory Objects: Resource=1495 Locks=671 SQLCache=69 Replication=2 LockBytes=2 ServerGlobal=43 Xact=21
2004-02-26 07:36:21.24 spid52 Query Memory Manager: Grants=1 Waiting=0 Maximum=150588 Available=1992
Note The index that is being created must reside in a database that is either set to the simple recovery model or to the bulk logged recovery model.

RESOLUTION

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

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     
   30-Jan-2004  16:29  2000.80.911.0      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
   03-May-2003  01:56                      1,581  Inst_repl_hotfix.sql
   30-Jan-2004  16:29  2000.80.911.0      90,692  Msgprox.dll      
   01-Apr-2003  02:07                      1,873  Odsole.sql
   30-Jan-2004  16:29  2000.80.911.0      62,024  Odsole70.dll     
   30-Jan-2004  16:29  2000.80.911.0      25,144  Opends60.dll     
   30-Jan-2004  16:28  2000.80.911.0      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
   30-Jan-2004  01:16                  1,090,380  Replmerg.sql
   30-Jan-2004  16:29  2000.80.911.0     221,768  Replprov.dll     
   30-Jan-2004  16:29  2000.80.911.0     307,784  Replrec.dll      
   29-Jan-2004  23:24  2000.80.911.0     159,813  Replres.rll
   06-Sep-2003  00:00                  1,087,150  Replsys.sql
   13-Aug-2003  16:28                    986,603  Repltran.sql
   30-Jan-2004  16:29  2000.80.911.0     287,304  Rinitcom.dll     
   30-Jan-2004  16:29  2000.80.911.0      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
   05-Feb-2004  00:46  2000.80.913.0      28,672  Sqlagent.dll     
   05-Feb-2004  00:47  2000.80.913.0     311,872  Sqlagent.exe     
   19-Feb-2004  18:02  2000.80.916.0     168,001  Sqlakw32.dll     
   30-Jan-2004  16:29  2000.80.911.0   4,215,360  Sqldmo.dll       
   07-Apr-2003  17:44                     25,172  Sqldumper.exe    
   29-Jan-2004  23:17  2000.80.911.0      28,672  Sqlevn70.rll
   05-Mar-2004  17:13  2000.80.922.0     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       
   30-Jan-2004  16:29  2000.80.911.0      57,920  Sqlrepss.dll     
   09-Mar-2004  19:54  2000.80.922.0   7,614,545  Sqlservr.exe     
   30-Jan-2004  16:29  2000.80.911.0     590,396  Sqlsort.dll      
   30-Jan-2004  16:29  2000.80.911.0      45,644  Sqlvdi.dll       
   30-Jan-2004  16:29  2000.80.911.0     106,588  Sqsrvres.dll     
   30-Jan-2004  16:29  2000.80.911.0      33,340  Ssmslpcn.dll     
   30-Jan-2004  16:29  2000.80.911.0      82,492  Ssnetlib.dll     
   30-Jan-2004  16:29  2000.80.911.0      25,148  Ssnmpn70.dll     
   28-Oct-2003  04:21  2000.80.873.0     123,456  Stardds.dll      
   30-Jan-2004  16:29  2000.80.911.0     158,240  Svrnetcn.dll     
   30-Jan-2004  16:29  2000.80.911.0      76,416  Svrnetcn.exe     
   30-Apr-2003  23:52  2000.80.816.0      45,132  Ums.dll          
   30-Jan-2004  16:29  2000.80.911.0      98,872  Xpweb70.dll

Note Because of file dependencies, the most recent hotfix or feature that contains these files may also contain additional files.

Note To enable the hotfix, you must enable the trace flag 3940. To enable the trace flag dynamically, run the DBCC TRACEON(-1,3940) command just before you rebuild the index. Then, disable the trace flag by running the DBCC TRACEOFF(-1,3940) command.

MORE INFORMATION

When a database uses the simple recovery model or the bulk logged recovery model, all dirty pages must be written to disk before the transaction commits. Dirty pages are pages that have been modified but not yet written to disk. SQL Server uses a mechanism that issues asynchronous write requests after a certain number of pages have been modified, even before the transaction commits. In the commit logic, the database engine waits for all asynchronous write requests to complete. However, SQL Server does not use any type of throttling mechanism to limit the number of outstanding asynchronous write requests.

In the circumstances where this problem occurs, the CREATE INDEX operation was building a new nonclustered index immediately after the operation built a clustered index, and the table fit in the cache. Additionally, the table size permitted the CREATE INDEX process to perform an in-memory sort. No intermediate sorted runs must be written to disk. Therefore, the index creation process can read, sort, and dirty pages at a very high rate. The combination of many stolen buffers that were being used for the sort and the lack of throttle in issuing the write operations may cause the whole address space of mappable buffers to be temporarily unavailable.

To resolve this problem, trace flag 3940 was added. Trace flag 3940 throttles the number of concurrent asynchronous write requests to 1,024. When this trace flag is enabled, the code that is flushing dirty pages for that transaction waits for every 1,024th write operation to complete before the code issues additional write requests. This throttling might theoretically cause a very small performance degradation. Because the problem occurs in very few cases, Microsoft decided to fix this problem by using a trace flag so that any customer who does not receive the BPool::Map warning is not affected by the possible performance difference.

This problem may theoretically occur because of an operation other than a CREATE INDEX operation, but other causes have not been discovered. To confirm that this bug was the likely cause of the BPool::Map warning, look for the following additional symptoms from the DBCC MEMORYSTATUS output in the SQL Server error log:

Buffer Distribution: Stolen is a large value and typically accounts for at least one third of the mappable buffers. The exact mappable count depends on many factors, including whether Microsoft Windows is running with the /3GB switch and the physical memory in the computer. Generally, the mappable count is around 200 thousand for a 2 GB address space and around 320 thousand for a 3 GB address space.
The difference between the Query Memory Manager: Maximum value and the Query Memory Manager: Available value is typically within several thousand of the stolen value.
Buffer Distribution: Dirty is large, typically more than 80 thousand buffers.

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