Snaservr.exe Traps While Starting More Than 50 Connections (194594)

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.