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Q142037: SNA Server Fails to Release Memory in SNA TCP/IP Interface DLL

Article: Q142037
Product(s): Microsoft SNA Server
Version(s): WINDOWS:2.1,2.11
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft SNA Server, versions 2.1, 2.11, on platform(s):
   - the operating system: Microsoft Windows NT 
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

A Windows NT Server running SNA Server 2.11 slows down when running SNA Server
clients that use TCP/IP.

This problem occurs sporadically.

CAUSE
=====

An SNA Server Service internal trace shows that SNA Server TCP/IP asynchronous
writes are not completing. These pending writes continue to consume system
memory. The SNA Server client configured for TCP/IP may continuously attempt to
open a session with the SNA Server. The SNA Server tries to send a response but
the write never completes and is unable to release the i/o (input/output) buffer
memory.

RESOLUTION
==========


SNAIP.DLL now aborts a connection if the connection has more than 100 pending
writes queued. Every time a connection is aborted, an event 706 is logged in the
application log:

  

  Event Id: 706

  Description:
  Connection to client %2 has been aborted due to too many (%1) pending
  writes.

  Explanation

  SNA Server has aborted a TCP/IP connection because asynchronous writes
  queued on the connection have not completed.

  ACTION

  Provide network support personnel with the event log file(s) related to
  SNA, and SNA internal trace file(s). For information about SNA log and
  trace files, see the "Microsoft SNA Server Administration Guide."

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

You can configure the abort limit by adding the MaxPendingWrites registry
parameter:

1. Go to the HKEY_LOCAL_MACHINE subtree under the following subkey:

  System\CurrentControlSet\Services\SnaBase\Parameters\SnaTcp

  If the SnaTcp subkey does not exist, it will need to be added it before going
  onto the next step.

2. Add the following information:

  Value Name: MaxPendingWrites
     Data Type:  REG_DWORD
     Data:       <value> (decimal)

  where <value> is by default 100 (decimal) with the updated SNAIP.DLL
  file (see below) installed.

Microsoft has updated the following files to correct this problem:

  <snaroot>\SYSTEM\SNAIP.DLL
  <snaroot>\SYSTEM\SNAEVENT.DLL

STATUS
======

Microsoft has confirmed this to be a problem in SNA Server for Windows NT. This
problem was corrected in the latest SNA Server for Windows NT, 2.11 U.S. Service
Pack. For information on obtaining the Service Pack, query on the following word
in the Microsoft Knowledge Base (without the spaces):

  S E R V P A C K

Additional query words: prodsna

======================================================================
Keywords          : kbnetwork 
Technology        : kbAudDeveloper kbSNAServSearch
Version           : WINDOWS:2.1,2.11
Issue type        : kbbug
Solution Type     : kbfix

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