SNA Server Status Shows "Off Line" Even Though It's Active

• Microsoft SNA Server, version 3.0 SP2

SYMPTOMS

After upgrading to SNA Server 3.0 Service Pack 2, SNA Manager may show the SNA Server (or TN3270, TN5250 or Print Service) status as "Off Line" even though the service(s) may be running correctly.

The onset of the "Off Line" status normally coincides with an access violation in the SNA Manage Agent service (mngagent.exe), though sometimes the service does appear to be running, the service fails to stop. When the service fails with an access violation, the following symptoms occur:

- The SNA Manage Agent service may no longer be running

- The following entry may appear in the <ntroot>\drwtsn32.log file:

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

  [...]

  function: RtlDestroyHeap
        77f7d339 83c40c           add     esp,0xc
        77f7d33c 57               push    edi
        77f7d33d e83af00000       call    RtlpNtEnumerateSubKey+0x312a 
        77f7d342 c6451400         mov     byte ptr [ebp+0x14],0x0      
        77f7d346 8b4d08           mov     ecx,[ebp+0x8]          
        77f7d349 0fb707           movzx   eax,word ptr [edi]         
        77f7d34c 294128           sub     [ecx+0x28],eax         
        77f7d34f 8b4e08           mov     ecx,[esi+0x8]          
        77f7d352 8b460c           mov     eax,[esi+0xc]          
        77f7d355 3bc8             cmp     ecx,eax
FAULT ->77f7d357 8908             mov     [eax],ecx 

   Function Name
   ntdll!RtlDestroyHeap 
   ntdll!LdrGetDllHandle 
   ntdll!RtlAllocateHeap 
   msvcrt!realloc 
   ws2_32!getservbyname 
   ws2_32!gethostname 
   snaip!BuildNosBlock  
   snadmod!BuildActiveNosBlocks  
   snadmod!SendDatagramTo  
   snamanag!SendDomainMailslot  
   snamanag!SNAStopService  
   mngsna!CNodeServe::OnCommand  
   mngbase!CNotifyQueue::Dispatch  
   mngbase!CNotifyQueue::ProcessWait  
   mngsna!DoMngSna

CAUSE

In some cases, the SNA Manage Agent was not allocating sufficient memory to hold management status information, causing internal buffers to be overwritten. This problem was causing memory heap corruption within the Manage Agent service which could cause the service to deadlock or fail with an access violation.

STATUS

Obtain the following fix or wait for the next SNA Server 3.0 Service Pack.

This fix should have the following timestamp:

  12/05/97  04:02p            97,104 <snaroot>\system\mngagent.exe
  12/05/97  04:02p           136,764 <ntroot>\symbols\exe\mngagent.dbg
  11/21/97  05:45p           362,128 <snaroot>\system\mngbase.dll

Microsoft has confirmed this to be a problem in SNA Server 3.0 Service Pack 2. This problem is fixed in SNA Server 4.0.

A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

Keywords          : prodsna snamanager snaprintservice snaserverservice snatn3270 snatn5250 kbbug3.00.sp2
Version           : WINDOWS:3.0SP2
Platform          : WINDOWS
Issue type        : kbbug
Solution Type     : kbfix kbpatch