Access Violation in Snalink.exe Activating Numerous Connections

ID: Q198398

The information in this article applies to:

Microsoft SNA Server, versions 3.0, 4.0
Microsoft SNA Server version 3.0 Service Packs 1, 2, and 3
Microsoft SNA Server version 4.0 Service Pack 1

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.

SYMPTOMS

An access violation in Snalink.exe may occur if numerous 802.2 Data Link Control (DLC) connections are activated concurrently in SNA Server Manager. The number of connections that have to be activated for this problem to occur varies, however it is more likely to occur when activating 50 or more 802.2 DLC connections concurrently. If Drwtsn32.exe is configured as the default debugger on the SNA Server system, the Drwtsn32.log file will be generated that contains entries similar to the following when this access violation occurs:

Application exception occurred: App: exe\snalink.dbg (pid=<process ID>) When: <date> @ <time> Exception number: c0000005 (access violation)

[...]

function: DlcGetDlcApiBuffer

[...]

6338a427 75fb jnz DlcGetDlcApiBuffer+0x54 (6338a424) FAULT ->6338a429 8b08 mov ecx,[eax] ds:00000000=???????? 6338a42b 898a18020000 mov [edx+0x218],ecx ds:000abe08=00000000

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

FramePtr ReturnAd Param#1 Param#2 Param#3 Param#4 Function Name 0104fef0 6338a1aa 00090013 00000001 0104ff28 00000027 snadlc!DlcGetDlcApiBuffer (FPO: [3,0,3])

-or-

Application exception occurred: App: exe\snalink.dbg (pid=<process ID>) When: <date> @ <time> Exception number: c0000005 (access violation)

[...]

function: CopyMessageToDlcBuffers

[...]

6338a20d 8b4c2424 mov ecx,[esp+0x24] ss:01f5e90b=???????? FAULT ->6338a211 66894104 mov [ecx+0x4],ax ds:00f15a07=???? 6338a215 8b542424 mov edx,[esp+0x24] ss:01f5e90b=????????

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

FramePtr ReturnAd Param#1 Param#2 Param#3 Param#4 Function Name 01ad7bdc 0072000a 60000400 38313062 806b0035 13003100 snadlc!CopyMessageToDlcBuffers (FPO: [EBP 0x00000000] [3,3,4])

CAUSE

The SNA DLC Link service (Snadlc.dll) does not correctly handle errors that it receives when the link service internal Logical Link Control (LLC) buffer pool is exhausted. The failure to correctly handle these errors causes the access violation in Snalink.exe.

RESOLUTION

SNA Server 4.0

To resolve this problem, obtain the latest service pack for SNA Server version 4.0. For additional information, please see the following article in the Microsoft Knowledge Base:

Q215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack

SNA Server 3.0

To resolve this problem, obtain the latest service pack for SNA Server version 3.0. For additional information, please see the following article in the Microsoft Knowledge Base:

Q184307 How to Obtain the Latest SNA Server Version 3.0 Service Pack

WORKAROUND

Instead of activating all of the configured 802.2 DLC connections concurrently, activate them individually or in smaller groups.

STATUS

Microsoft has confirmed this to be a problem in SNA Server versions 3.0 and 4.0. This problem was first corrected in SNA Server version 3.0 Service Pack 4 and SNA Server version 4.0 Service Pack 3.

MORE INFORMATION

After you apply the update, the 802.2 DLC Link service will not generate an access violation when activating numerous connections. However, some of the connections may not activate (they will be in an Inactive state) or some of the LUs (Logical Units) defined on the connections may stay in an Inactive state. This can occur when the LLC buffer pool is exhausted. If it appears that the LLC buffer pool is too small, it can be increased by setting the following registry entry:

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

Start Registry Editor (Regedt32.exe).

Locate the following key in the registry: HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/<snadlcX> /Parameters/ExtraParameters/ where <snadlcX> is the link service name (that is, SnaDlc1, SnaDlc2, and so forth). NOTE: The above registry key is one path; it has been wrapped for readability.

On the Edit menu, click Add Value, and then add the following registry value:


      Value Name: LlcBufferPoolSize
      Data Type:  REG_DWORD
      Value:      &lt;pool size in bytes&gt;

   The default pool size is 1024000. If the buffer pool is being exhausted,
   a value of 4096000 will allow a larger pool that should allow more
   connections to be started concurrently.

Quit Registry Editor.

The SnaDlcX link service must be stopped and started for this change to take effect. This can be accomplished by stopping and starting the SNA Server service. However, if SnaDlcX has been distributed for use with the SNA distributed link service, the SnaDlcX service must be manually stopped and started.

For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base:

Q216047 Activating Numerous DLC Connections Results in Inactive LUs

Additional query words:

Keywords : sna3sp4fix sna4sp3fix
Version : WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,4.0,4.0SP1
Platform : WINDOWS
Issue type : kbbug