Microsoft KB Archive/178492

= SNA 3.0 TN3270 or TN5250 Server Traps When Configuration Saved =

Article ID: 178492

Article Last Modified on 9/22/2005

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APPLIES TO


 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 3.0 Service Pack 2

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This article was previously published under Q178492



SYMPTOMS
The TN3270 or TN5250 service may end unexpectedly with an access violation when saving the configuration file, even if the configuration file changes do not affect these services. This problem can occur if the SNA Server Manage Agent service (Mngagent.exe) is restarted on the SNA Server. The following symptoms will occur when this problem happens:  All TN3270 or TN5250 client users will lose their sessions and the TN3270 or TN5250 Server service will no longer be running. The following event will be logged in the Windows NT application event log:

  Event ID: 624 Source:  TN3270 Server (or TN5250 Server) Description: Creating dump file \traces\snadump.log for 

 A new entry will be created in the \drwtsn32.log file (the failing routine in mngbase.dll is the same for both TN3270 or TN5250):

  Application exception occurred: App: exe\tn3servr.dbg Exception number: c0000005 (access violation)

[...]

State Dump for Thread Id

eax=0c9dfda4 ebx=77e7a69f ecx=0b5f0000 edx=42008000 esi=00000003 edi=00000003 eip=6098d4c8 esp=0c9dfd98 ebp=77e719c8 iopl=0 nv up ei pl nz na po nc  cs=001b  ss=0023  ds=0023  es=0023  fs=0038  gs=0000 efl=00000206

function: MngGetRectypeChangeMask 6098d4a6 6a00            push    0x0 6098d4a8 682c1400c0      push    0xc000142c 6098d4ad 6a01            push    0x1 6098d4af e8fc010000      call    MngReportToEventLog (6098d6b0) 6098d4b4 33c0            xor     eax,eax 6098d4b6 33d2            xor     edx,edx 6098d4b8 5e              pop     esi 6098d4b9 81c4a0000000    add     esp,0xa0 6098d4bf c20400          ret     0x4 6098d4c2 81e6ffff0000    and     esi,0xffff FAULT ->6098d4c8 8b84f1a0010000  mov     eax,[ecx+esi*8+0x1a0]

*> Stack Back Trace <*

Function Name

mngbase!MngGetRectypeChangeMask mngbase!MngIsRectypeChanged mngext!Mng_IsRectypeChanged tn3servr!Tn3ManageActionEx tn3servr!Tn3ManageActionEx tn3servr!Tn3ManageActionEx mngext!CMngExtSink::OnCommand mngbase!CNotifyQueue::Dispatch mngbase!CNotifyQueue::ProcessWait mngext!Mng_IsRectypeChanged kernel32!BaseThreadStart tn3  servr!





CAUSE
When the configuration file changes, the TN3270 and TN5250 services are both notified and attempt to handle dynamic changes to their configuration data. However, if the mngagent service had been stopped and restarted, the configuration data location within the Manage shared memory may change, causing the services to access an invalid memory location causing an access violation.



WORKAROUND
Do not stop and restart the SNA Server Manage Agent service (Mngagent.exe).



STATUS
Microsoft has confirmed this to be a problem in SNA Server 3.0 (including SP1 and SP2).

This problem was corrected in the latest SNA Server version 3.0 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

Keywords: kbbug kbfix kbqfe kbhotfixserver KB178492

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