Microsoft KB Archive/180054

= Perfmon Trap or Winlogon STOP C000021A When Running Perfmon =

Article ID: 180054

Article Last Modified on 9/22/2005

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APPLIES TO


 * Microsoft SNA Server 4.0

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This article was previously published under Q180054



SYMPTOMS
When you start the Windows NT Server Performance Monitor locally on a computer running SNA Server and you pressing the "+" key (which loads the extension Performance Monitor DLLs, including snaperf.dll), the following errors may occur:  All Performance Monitor objects and counters are blank, even SNA Server ones. When you start Performance Monitor under a debugger, it indicates that the Performance Monitor heap is corrupted. This causes Performance Monitor (Perfmon.exe) to encounter an access violation (0xC0000005). When you start Performance Monitor on another system, focus on the computer running SNA Server 4.0, and press the "+" key, an access violation (0xC0000005) occurs in Winlogon.exe, leading to a STOP 0xC000021A. The following log entry may appear in the \drwtsn32.log file:

Application exception occurred:

App: exe\winlogon.dbg ()

Exception number: c0000005 (access violation)

[...]

function: RtlAllocateHeap

[...]



NOTE: A similar access violation problem may occur with SNA Server 3.0, though this problem is fixed when applying 3.0 Service Pack 2.



CAUSE
This problem is caused by a regression introduced in SNA Server 4.0 when support for multiple instances of the SNA Server service on a single computer was added. However, multiple SNA Server services do not need to be configured in order to encounter this problem.



WORKAROUND
Do not run Windows NT Performance Monitor against SNA Server.



STATUS
Microsoft has confirmed this to be a problem in SNA Server version 4.0. This problem was corrected in the latest SNA Server version 4.0 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K



MORE INFORMATION
For additional information on the access violation problem may with SNA Server 3.0, please see the following article in the Microsoft Knowledge Base:

169488 Errors When Performance Monitoring SNA Server

Keywords: kbbug kbfix kbqfe kbhotfixserver KB180054

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