Knowledge Base

SNA 3.0 TN3270 or TN5250 Server Traps When Configuration Saved

Article ID: 178492

Article Last Modified on 9/22/2005

APPLIES TO

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

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 <snaroot>\traces\snadump.log for 
                <tn3servr.exe | tn5250.exe >

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

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

   [...]

   State Dump for Thread Id <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!<nosymbols>

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

Microsoft KB Archive/178492

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