Microsoft KB Archive/149924

= TN3270 Session Fail w/Sense 2004 if TN3270E Server Stressed =

Article ID: 149924

Article Last Modified on 11/19/2003

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APPLIES TO


 * Microsoft SNA Server 3.0, when used with:
 * Microsoft Windows NT 4.0
 * Microsoft SNA Server 2.11 Service Pack 1, when used with:
 * Microsoft Windows NT 4.0

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This article was previously published under Q149924





SYMPTOMS
When the TN3270E server is under heavy client stress, a TN3270 session may stop receiving data from the host. The Microsoft Windows NT Application Event Log will log the following message:

Event ID: 21

Description: Negative Response Sent on Connection xxxx (SENSE = 2004)

where xxxx is the name of the SNA Server connection being used to host communication.



CAUSE
The TN3270E Server uses the RUI interface to communicate with the mainframe using RUI_READ and RUI_WRITE verbs. The RUI interface is asynchronous with completion notified via NT events. The normal sequence of verbs is the following:
 * issue RUI_READ - read waiting for data from host.
 * issue RUI_WRITE - send data to host.
 * RUI_WRITE completes - data has been sent to the host.
 * RUI_READ completes - the host has sent data in response.

When this problem occurs, this is the sequence of verbs as the TN3270E Server sees it:
 * issue RUI_READ - read waiting for data from host.
 * issue RUI_WRITE - send data to host.
 * RUI_READ completes - the host has sent data in response.
 * RUI_WRITE completes - data has been sent to the host.

The TN3270E Server is receiving notification of the RUI_READ verb completing before it receives notification of the RUI_WRITE verb completing, although the RUI_WRITE did complete before the RUI_READ. Although this is not usual behavior, Windows NT does not guarantee the order in which events are processed. The TN3270E Server is not able to handle a RUI_READ completing while the RUI_WRITE is still outstanding, and it treats the case as an error.



RESOLUTION
The TN3270E Server has been updated so that it will queue up an RUI_READ completion if it occurs while an RUI_WRITE is still pending. It will then process the RUI_READ completion after processing the RUI_WRITE completion.

The following files have been modified:

\TN3270\TN3NTMSG.DLL

\TN3270\TN3SERVR.EXE

\TN3270\TNADMIN.EXE

This fix is for the TN3270E Server that is included with SNA Server 2.11 Service Pack 1. If this problem occurs with the TN3270 Server shipped with SNA Server 2.11, apply Service Pack 1 before applying these fixes.



STATUS
Microsoft has confirmed this to be a problem in SNA Server versions 2.11 and 2.11 SP1. This problem was corrected in the latest Microsoft SNA Server 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: kbbug kbfix kbnetwork KB149924

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