DOCUMENT:Q194594  01-MAR-2001  [sna]
TITLE   :Snaservr.exe Traps While Starting More Than 50 Connections
PRODUCT :Microsoft SNA Server
PROD/VER::3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1
OPER/SYS:
KEYWORDS:kbfixlist

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The information in this article applies to:

 - Microsoft SNA Server, versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1 
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SYMPTOMS
========

The SNA Server service (Snaservr.exe) may experience a hardcoded breakpoint
application exception if it is configured to start 50 or more connections
simultaneously. If Drwtsn32.exe is configured as the default debugger for the
Windows NT system running SNA Server, the Drwtsn32.log file will contain
information similar to the following when this occurs:

   Application exception occurred:
        App: exe\snaservr.dbg (pid=<Process ID #)
        When: <date> @ <time>
        Exception number: 80000003 (hardcoded breakpoint)

   [data omitted...]

   function: DbgBreakPoint
   FAULT ->77f76148 cc               int     3
           77f76149 c3               ret
           77f7614a 8bc0             mov     eax,eax

   *----> Stack Back Trace <----*

   FramePtr ReturnAd Param#1  Param#2  Param#3  Param#4
   602012a0 55536021 57c08556 0102840f 15ff0000 60201050

   Function Name
   ntdll!DbgBreakPoint

NOTE: The above lines have been wrapped for readability.

In addition, SNA Server may log the following event in the Windows NT Application
Event Log when this occurs:

   Event ID: 102
   Source: SNA Server
   Description: (BC6) Internal Error

             Subcode Information:
             X'0B02' A dynamic storage allocation request has failed.
             X'0BC1' Buffer header pointer is corrupted.
             X'0BC3' Corruption of internal free buffer pool.
             X'0BC5' Free ready pool is empty.
             X'0BC6' Free active pool is empty.


CAUSE
=====

The application exception and Event 102 occur when the SNA Server service
depletes its free/ready pool, which is its internal list of threads that that
are waiting to be scheduled for execution. This pool can be depleted if there
are more than 50 connections trying to activate simultaneously.


RESOLUTION
==========

Microsoft has confirmed this to be a problem in SNA Server versions 3.0, 3.0
SP1, 3.0 SP2, 3.0 SP3, 4.0, and 4.0 SP1. We are researching this problem in SNA
Server version 3.0 and will post more information here in the Knowledge Base as
it becomes available.

This problem was corrected in the latest SNA Server version 4.0 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


WORKAROUND
==========

Connections can be configured for "On Demand" activation instead of for "On
Server Startup" activation so that all of the connections will not attempt to
start when the SNA Server service is started. "On Demand" connections will start
when a user requests a resource (such as a LU or LU Pool) that is defined on
that connection that is not already available on a previously activated
connection.

Additional query words:

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Keywords          :  kbfixlist
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ400 kbSNAServ300SP3 kbSNAServ300SP1 kbSNAServ400SP1 kbSNAServ300SP2
Version           : :3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1
Issue type        : kbbug
Solution Type     : kbfix

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Copyright Microsoft Corporation 2001.