FIX: DBCC TEXTALLOC May Cause SQL Server to Stop Responding

ID: Q248764

The information in this article applies to:

Microsoft SQL Server version 6.5 Service Pack 5a

BUG #: 18930 (SQLBUG_65)

SYMPTOMS

Under memory constrained conditions, running DBCC TEXTALLOC against a table containing large text values may cause SQL Server to stop processing queries and logon requests. SQL Server may also write indefinite bufwait messages or write an access violation stack dump to the errorlog in some cases.

1999/08/30 01:31:16.11 spid20 bufwait: timeout, BUF_IO, bp 0x4cbcc40, pg 0xee1c1, stat 0x801004/0x6, obj 0x269ab60b, bpss 0x48aaf98

SQL Server may not seem to be responding and will not allow processing until the service is stopped and restarted.

CAUSE

Read-ahead was being used for the text and not the base table.

RESOLUTION

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next SQL Server service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

The English version of this fix should have the following file attributes or later:


   Version     File name      Platform
   ------------------------------------

   6.50.467    sql467i.exe    Intel
   6.50.467    sql467a.exe    Alpha

NOTE: Due to file dependencies, the most recent hotfix or feature that contains the above files may also contain additional files.

This is not an issue in SQL Server 7.0 or later.

STATUS

Microsoft has confirmed this to be a problem in SQL Server version 6.5 Service Pack 5a.

MORE INFORMATION

The following error may be written to the errorlog, which may cause a concern for reconfiguring sp_configure settings:

1999/08/30 23:36:10.35 spid24 WARNING: no read ahead slots available. Use sp_configure to increase the number of slots ('RA worker threads' or 'RA slots per thread').

Increasing the read ahead settings may provide some immediate relief, but the likelihood of reoccurrence is increased as more text is added to the table.

Additional query words:

Keywords : kbSQLServ650sp5bug kbbug6.50.sp5
Version : winnt:6.5 Service Pack 5a
Platform : winnt
Issue type : kbbug