Microsoft KB Archive/824848

= FIX: An LU 6.2 Session Is Not Released After the RECEIVE_ALLOCATE Verb is Canceled =

Article ID: 824848

Article Last Modified on 10/26/2005

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APPLIES TO


 * Microsoft Host Integration Server 2000 Standard Edition
 * Microsoft Host Integration Server 2000 Service Pack 1
 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 4.0 Service Pack 1
 * Microsoft SNA Server 4.0 Service Pack 2
 * Microsoft SNA Server 4.0 Service Pack 3
 * Microsoft SNA Server 4.0 Service Pack 4

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SYMPTOMS
An LU 6.2 session may not be released after an invokable transaction program (TP) cancels an outstanding RECEIVE_ALLOCATE verb. When this behavior occurs, the LU 6.2 session that is affected is not available for use by any other advanced program-to-program communication (APPC) applications or by any other common programming interface for communications (CPI-C) applications.



CAUSE
The problem occurs because of a small timing window that exists if an invokable TP cancels an outstanding RECEIVE_ALLOCATE verb at the same time that the host application tries to invoke the TP.

When this timing window is encountered, although the request to cancel the RECEIVE_ALLOCATE verb is processed, the SNA Server service is not informed of the cancellation request. The result is that the SNA Server service does not inform the host application that the session request has been canceled. The LU 6.2 session is left in its current state and is unavailable for use.



RESOLUTION
This section contains information about fixes for:
 * SNA Server 4.0
 * Host Integration Server 2000

SNA SERVER 4.0
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft SNA Server 4.0 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.   Date         Time   Version      Size   File name --  30-Jul-2003  20:59  4.0.0.608   11,056  Fmistr32.dll 30-Jul-2003 20:59  4.0.0.608   46,304  Snaat.dll 30-Jul-2003 20:59  4.0.0.608   58,672  Snabv.dll 30-Jul-2003 20:59  4.0.0.608  515,824  Snadmod.dll 30-Jul-2003 20:59  4.0.0.608  233,760  Snaevent.dll 30-Jul-2003 20:59  4.0.0.608   69,168  Snaip.dll 30-Jul-2003 20:59  4.0.0.608   44,816  Snalm.dll 30-Jul-2003 20:59  4.0.0.608   48,336  Snanb.dll 30-Jul-2003 20:59  4.0.0.608   12,752  Snancp.dll 30-Jul-2003 20:59  4.0.0.608   60,832  Snanw.dll 30-Jul-2003 20:59  4.0.0.608    8,640  Vstapi.dll

Note Because of file dependencies, the most recent fix that contains the preceding files may also contain additional files.

Service pack information
To resolve this problem, obtain the latest service pack for Microsoft Host Integration Server 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

328152 How to obtain the latest service pack for Host Integration Server 2000

Hotfix information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.   Date         Time   Version      Size    File name --  31-Jul-2003  19:37  5.0.0.932    20,752  Fmistr32.dll 31-Jul-2003 19:37  5.0.0.932    53,520  Snaat.dll 31-Jul-2003 19:37  5.0.0.932    69,904  Snabv.dll 31-Jul-2003 19:37  5.0.0.932   557,328  Snadmod.dll 31-Jul-2003 19:37  5.0.0.932   483,600  Snaevent.dll 31-Jul-2003 19:37  5.0.0.932    82,192  Snaip.dll 31-Jul-2003 19:37  5.0.0.932    49,424  Snalm.dll 31-Jul-2003 19:37  5.0.0.932    20,752  Snancp.dll 31-Jul-2003 19:37  5.0.0.932    65,808  Snanw.dll 31-Jul-2003 19:37  5.0.0.932    16,656  Vstapi.dll

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



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.

This problem was corrected in Microsoft Host Integration Server 2000 Service Pack 2.



MORE INFORMATION
The following sequence of events may lead to the problem that is described in this article:
 * 1) The invokable TP issues a RECEIVE_ALLOCATE verb to listen for an incoming conversation request.
 * 2) The invoking mainframe application issues a function management header 5 (FMH-5) ATTACH to invoke a conversation with the invokable TP.
 * 3) The SNA Server service's dynamic access module (DMOD, the Client/Server interface) sends a dynamic load (DLOAD) request to the Host Integration Server 2000 client where the invokable TP is running.

At the same time that the Host Integration Server 2000 client receives the DLOAD request from the SNA Server service, the invokable TP cancels the RECEIVE_ALLOCATE verb by using a WinAPPCCancelAsyncRequest verb.
 * 1) The Host Integration Server 2000 client sends a Close Error Request to the DMOD of the SNA Server service.
 * 2) The SNA Server service's DMOD receives the Close Error Request that is immediately followed by a DLOAD_STATUS(Success) message. These two messages are received at the same time (according to the timestamp in the Host Integration Server 2000 traces that captured the problem).
 * 3) Upon receipt of the DLOAD_STATUS(Success) message, the SNA Server service tries to send an Open LU62 Request to the Host Integration Server 2000 client where the invokable TP is running.
 * 4) The following lists events that do not occur:
 * 5) * The Open LU62 Request is not sent to the Host Integration Server 2000 client because the connection to the client was closed because of the Close Error Request.
 * 6) * The SNA Server service was not notified of the Close Error Request because of the timing window that exists.
 * 7) * The Open LU62 Request is not canceled and an error message is not sent to the host application.

The LU 6.2 session is not available for use with any other APPC or CPI-C applications until one of the following occurs:
 * The mainframe application sends an UNBIND to deactivate the session.

- or -
 * The host connection on the Host Integration Server 2000 server is stopped and restarted.

Keywords: kbbug kbfix kbqfe kbhotfixserver KB824848

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