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Q193813: Multiple NVRunCmd Commands May Cause Unpredictable Results

Article: Q193813
Product(s): Microsoft SNA Server
Version(s): 2.11,2.11 SP1,2.11 SP2,3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1
Operating System(s): 
Keyword(s): kbbuglist
Last Modified: 24-OCT-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft SNA Server, versions 2.11, 2.11 SP1, 2.11 SP2, 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1 
-------------------------------------------------------------------------------

SYMPTOMS
========

An SNA Server may experience unpredictable behavior if it receives multiple
NVRunCmd commands from the host over one of its configured host connections.
This will only occur if the SNA Server receives NVRunCmd commands while it is
currently processing a previous NVRunCmd.

The following is a sequence that caused the PU (Physical Unit) defined in VTAM
for a SNA Server host connection to hang:

  Host                                    SNA Server
  ----                                    ----------

  (1) NMVT (DIR D:\SNA\SYSTEM\*.*)  ->
  (2) NMVT (DIR C:\*.*)             ->
                                    <-     (2) NMVT -RSP (Sense 084B0003)
                                    <-     (1) Data (1st portion of data)
  (3) NMVT (DIR C:\*.*)             ->
                                    <-     (1) (Final data for NMVT #1)

In this sequence, the host sends three NVRunCmds over the connection defined in
SNA Server. The first NVRunCmd command (designated as number 1) is accepted, and
eventually completes, returning the contents of the D:\Sna\System directory. The
second NVRunCmd command (designated as number 2), is rejected by SNA Server.
This request is rejected with an IBM Sense Code of 084B0003, which indicates
that the requested resources are not available. SNA Server does not respond to
the third NVRunCmd command (designated as number 3) at all. The lack of response
is what causes the PU defined for this host connection to hang.

It is possible that other symptoms may also occur since SNA Server is not
correctly handling multiple concurrent NVRunCmd commands.

CAUSE
=====

The NVRunCmd service is designed to process only one command at a time. If
subsequent commands are received while a previous command is being processed,
the subsequent NVRunCmd commands will be rejected by SNA Server.

The problem is that the SNA Server service doesn't properly handle the case when
multiple NVRunCmd commands are received at the same time. When this occurs, the
SNA Server may correctly reject one or more of the commands it receives while
processing the initial request. However, it may also attempt to process one of
the NVRunCmd commands while the initial request is still processing, and this
can lead to unpredictable results such as the PU hanging.


RESOLUTION
==========

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:

  Q219049 How to Obtain SNA Server Version 3.0 Service Pack 4



SNA Server 4.0
--------------

Microsoft has confirmed this to be a problem in SNA Server version 4.0 and 4.0
SP1. 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


STATUS
======

Microsoft has confirmed this to be a problem in SNA Server versions 2.11, 2.11
SP1, 2.11 SP2, 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, and 4.0 SP1. This problem
was first corrected in SNA Server 3.0 Service Pack 4.

MORE INFORMATION
================

After applying the hotfix for this problem, SNA Server will reject all
subsequent NVRunCmd commands if a NVRunCmd command is being processed.

For more information on the NVRunCmd service, please refer to one of the
following:

- SNA Server Administration Guide - SNA Server Online Help

Additional query words:

======================================================================
Keywords          :  kbbuglist
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ211 kbSNAServ400 kbSNAServ211SP1 kbSNAServ211SP2 kbSNAServ300SP3 kbSNAServ300SP1 kbSNAServ400SP1 kbSNAServ300SP2
Version           : :2.11,2.11 SP1,2.11 SP2,3.0,3.0 SP1,3.0 SP2,3.0 SP3,4.0,4.0 SP1
Issue type        : kbbug
Solution Type     : kbfix

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