Microsoft KB Archive/170437

= FIX: Multi-Session DBCC OUTPUTBUFFER Under Stress Causes AV =

Article ID: 170437

Article Last Modified on 10/16/2003

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APPLIES TO


 * Microsoft SQL Server 6.0 Standard Edition
 * Microsoft SQL Server 6.5 Standard Edition

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This article was previously published under Q170437



BUG #: 17005 (6.5) 15719 (6.0)



SYMPTOMS
Running frequent DBCC OUTPUTBUFFER commands from more than one concurrent session while the system is under transactional stress may cause a handled access violation (AV). After this AV, the server may stop responding. This problem happens on all versions of SQL Server from 6.00.121 through 6.50.258, but it only happens on:


 * SMP computers with three or more processors.
 * Two-processor computers with smp concurrency set to -1.

If you are running a debug server (needed for accurate stack traces on SQL Server 6.5), you can identify the problem by one of the following two call stacks from 6.50.255 debug:

The following stack is less frequent:

  debugSR!ubchkalloc+0x22 debugSR!memshrink+0xb8 debugSR!s_pop+0x23e debugSR!s_pop+0xb9 debugSR!execproc+0x11eb debugSR!execrpc+0xd07

The following stack is more frequent:

  debugSR!ubfree+0x96 debugSR!memfree+0x215 debugSR!procfree+0xc8 debugSR!procrm2+0x17a debugSR!procrm+0xd7 debugSR!s_pop+0x22d debugSR!s_pop+0xb9 debugSR!s_cleanframe+0x2fb debugSR!s_recompile+0x942 debugSR!ex_raise+0x37a debugSR!prepscan_failed+0x23 debugSR!prepscan+0x367 debugSR!startscan+0x377 debugSR!exec_substitute+0x435 debugSR!exec_eop+0x493 debugSR!exec_eop+0x1e2 debugSR!execute+0x2c0 debugSR!s_execute+0xbf8 debugSR!sequencer+0x35c



WORKAROUND
To work around this problem, do not issue multiple concurrent DBCC OUTPUTBUFFER statements.



STATUS
Microsoft has confirmed this to be a problem in SQL Server versions 6.0 and 6.5. This problem was corrected in the latest Microsoft SQL Server 6.5 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

  S E R V P A C K

Additional query words: hang hung freeze frozen dead stopped

Keywords: kbbug kbfix kbenv kbusage KB170437

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