SNA Server Fails Due to Access Violation in SNADMOD!RpcRouteProc

ID: Q230204

The information in this article applies to:

Microsoft SNA Server, versions 3.0, 3.0SP1, 3.0SP2, 3.0SP3, 4.0, 4.0SP1, 4.0SP2

SYMPTOMS

The SNA Server service (Snaservr.exe) may fail unexpectedly or may stop accepting new client connections when the access violation in SNADMOD!RpcRoutProc occurs. This results in one or both of the following:

Previously-connected users lose their host (mainframe or AS/400) sessions.
New users are unable to obtain a new host session.

If the Windows NT Server where SNA Server is running is configured with Drwtsn32.exe as the default debugger, a Drwtsn32.log entry may be generated when this failure occurs, indicating a FAULT in the top-level routine along with the following stack-back trace (which may vary):


    snadmod!RpcRouteProc+0x400
    snadmod!sepdq2_int+0x122
    ntdll!RtlLeaveCriticalSection+0x1d
    snadmod!sbpdin_int+0x23d
    snadmod!sbpdin+0x25
    snaservr!sbpcdin+0x50
    snaservr!sbpsched+0x2ac
    snaservr!sbpgmain+0x25
    snasvc!ServiceMainFunction+0x140
    advapi32!ScSvcctrlThreadA+0xe
    kernel32!BaseThreadStart+0x51

In the reported instances of this problem, the SNA Server systems had to be rebooted to recover.

CAUSE

The access violation occurs when an SNA Server RPC Response message is inadvertently routed to the SNA Server service. The SNA Server service is unable to interpret this message, which causes the access violation to occur.

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

A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://www.microsoft.com/support/supportnet/overview/overview.asp

The English version of this fix should have the following file attributes or later:

File name	Date	Time
Snadmod.dll	3/11/99	7:45PM
snaevent.dll	3/11/99	7:46PM

NOTE: Because of file dependencies, the most recent fix that contains the above files may also contain additional files.

NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee.

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

Q154871 Determining If You Are Eligible for No-Charge Technical Support

STATUS

Microsoft has confirmed this to be a problem in Microsoft SNA Server versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1, and 4.0 SP2. This problem was first corrected in SNA Server version 4.0 Service Pack 3.

MORE INFORMATION

An exception handler was added to handle this exception whenever it may occur. The SNA Server service will no longer fail unexpectedly or stop accepting client connections when this occurs after the update is applied. In addition, the following event will be logged in the Windows NT application event log if this problem occurs after the update is applied.

Event ID: 731
Description: Invalid RPC Response message
RPC Code: <value>
Source: <value>
Destination: <value>

Additional query words:

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