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Q193988: APPC/CPIC Application May Fail When Using Remote APPC LU Name

Article: Q193988
Product(s): Microsoft SNA Server
Version(s): WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,4.0,4.0SP1
Operating System(s): 
Keyword(s): kbfixlist
Last Modified: 20-OCT-2000

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The information in this article applies to:

- Microsoft SNA Server, versions 3.0, 3.0SP1, 3.0SP2, 3.0SP3, 4.0, 4.0SP1 
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SYMPTOMS
========

An Advanced Program-to-Program Communication (APPC) application may display the
following error message when attempting to allocate multiple conversations at
the same time:

  primary_rc = AP_COMM_SUBSYSTEM_NOT_LOADED (0xF004)
  secondary_rc = 0xF0000002

A Common Programming Interface for Communications (CPIC) application may receive
Error 20, or CM_PRODUCT_SPECIFIC_ERROR.

This error has been observed in the following scenario:

- If an APPC application specifies a NULL Local APPC LU alias in TP_STARTED,
  and a fully qualified Remote APPC LU name (instead of a Remote APPC LU alias)
  in [MC_]ALLOCATE. Or, if a CPIC application specifies a fully qualified
  Remote APPC LU name prior to calling CMALLC (Allocate).

- If the APPC or CPIC application attempts to allocate up to 10 concurrent
  requests within a second.

- If the APPC or CPIC application is running on an SNA Server Windows NT or
  Windows 95/98 client machine and there are several SNA Servers in the
  subdomain, where some of the servers may not be configured to support the
  Remote LU name being requested.


NOTE: There are many more common scenarios that can cause the above APPC or CPIC
return codes. For more information, please see the following Microsoft Knowledge
Base articles:

  Q148359 SNA Server APPC Error: F004 AP_COMM_SUBSYSTEM_NOT_LOADED


  Q132720 SNA Server CPIC Allocate Error 20(CM_PRODUCT_SPECIFIC_ERROR)


CAUSE
=====

When an APPC or CPIC application specifies a null Local LU alias, null Remote
APPC LU alias, and a fully qualified Remote APPC LU name, the SNA Server client
is not optimized to locate the appropriate SNA Server(s), so the SNA client
tries all SNA Servers in the subdomain. However, when the application attempts
to allocate multiple conversations at the same instant, the SNA client "server
resource location" may fail in some cases to try all servers, and return an
error to one or more of the allocation requests.

This problem does not occur when the application specifies a Local or Remote APPC
LU alias, because the SNA client determines which servers support the request,
and only tries those servers. This improvement has been implemented since the
release of SNA Server 2.11 Service Pack 2, but did not cover the case where only
the fully qualified Remote APPC LU name is specified by the APPC or CPIC
application.

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
--------------

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


WORKAROUND
==========

The APPC or CPIC application can solve this problem by specifying a Remote APPC
LU alias within the [MC_]ALLOCATE or CMALLC request.

STATUS
======

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


Additional query words:

======================================================================
Keywords          :  kbfixlist
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ400
Version           : WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,4.0,4.0SP1
Issue type        : kbbug
Solution Type     : kbfix

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