3270 Emulator Hangs and Returns X'1003' Error to Mainframe

ID: Q182915

The information in this article applies to:

Microsoft SNA Server, versions 3.0, 4.0

SYMPTOMS

A 3270 emulator may hang while receiving a screen of data from a mainframe. The emulator screen may be partially filled with data when the emulator hangs. The SNA Server computer that the emulator is connecting through logs a message similar to the following in its Application Event log:


   Event ID: 21
   Source: SNA Server
   Description: (1124) Negative Response Sent on Connection <connection
   name> (SENSE = 1003).

SUBCODE INFORMATION:
X'1124' A negative response was sent and logged. This error normally follows a more specific error message, depending on the type of negative response sent and its cause. The SNA sense data provides details about the type of error.

This problem does not occur if the emulator connects to a mainframe through SNA Server 3.0 SP2 and earlier.

In addition, this problem may not occur with all 3270 emulators. This problem has been reproduced using NetSoft's NS/Elite 3270 emulator. It could not be reproduced using the 3270 Applet included with SNA Server.

CAUSE

SNA Server 4.0 incorrectly sets the ECI (End Chain Indicator) and CDI (Change Direction Indicator) flags on the first segment of an RU (Request/Response Unit) sent to a 3270 emulator that has indicated that it can receive RU segments.

When delivering RU segments, EC (End Chain) and CD (Change Direction) indicators are supposed to be delayed if they occur in the RH (Request/Response Header) of the RU's first segment until the last segment of the RU is sent to the emulator.

This problem also occurs with SNA Server 3.0 SP3. The problem is caused because of a regression introduced by the fix addressing bug 9185, which was fixed in SNA Server 3.0 SP3 and the retail release of SNA Server 4.0. For more information about bug 9185, please see the following article in the Microsoft Knowledge Base:

Q178256: LUA Program Hangs After Receiving Exception Request (EXR)

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:

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

SNA Server 4.0

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 3.0 SP3 and 4.0. This problem was first corrected in SNA Server 3.0 Service Pack 4.

MORE INFORMATION

When you start a 3270 session, the 3270 emulator indicates whether it supports the delivery of RU segments. If the emulator supports the delivery of RU segments, SNA Server can send data it receives from a mainframe to the emulator as it is received. If the emulator indicates that it does not support the delivery of RU segments, SNA Server will not send the data it receives to the emulator until it receives the entire RU from the mainframe. The SNA Server service then assembles the data into a complete RU before sending it to the emulator. Please refer to the "Segment Delivery" section of the SNA Server 3270 Emulator Interface Specification manual for more details on this feature. This manual is included with the Online SDK Documentation shipped with SNA Server.

IBM sense codes are defined in the IBM SNA Formats Guide (GA27- 3136). Sense code X'1003' is defined as follows:

Function Not Supported: The function requested is not supported. The function may have been specified by a formatted request code, a field in an RU, or a control character.

NetSoft NS/Elite is manufactured by NetSoft, Inc., a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this product's performance or reliability.

Additional query words:

Keywords : kbbug4.00 prodsna sna3270
Version : WINDOWS:3.0,4.0
Platform : WINDOWS
Issue type : kbbug