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

• Microsoft SNA Server, versions 3.0 SP2, 4.0

SYMPTOMS

After upgrading to SNA Server 3.0 Service Pack 2, or upgrading to or installing SNA Server 4.0, 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 
  
  *----> Stack Back Trace <----*
  
     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

Microsoft has confirmed this to be a problem in SNA Server 3.0 Service Pack 2 and 4.0. This problem was corrected in the latest SNA Server versions 3.0 and 4.0 U.S. Service Packs. For information on obtaining these Service Packs, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

Additional query words:

Keywords : prodsna snatn3270 kbbug3.00.sp2 kbfix3.00.sp3 snamanager snaprintservice snaserverservice snatn5250
Version : WINDOWS:3.0 SP2,4.0
Platform : WINDOWS
Issue type : kbbug