Microsoft KB Archive/178493

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

Article ID: 178493

Article Last Modified on 9/22/2005

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APPLIES TO


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

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This article was previously published under Q178493



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 \drwtsn32.log file:  Application exception occurred: App: exe\mngagent.dbg 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

Keywords: kbbug kbfix kbqfe kbhotfixserver KB178493

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