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Q180938: Unable to Activate Multiple DLS Connections Using the Same SAP

Article: Q180938
Product(s): Microsoft SNA Server
Version(s): WINDOWS:3.0,3.0 SP1,3.0 SP2,4.0
Operating System(s): 
Keyword(s): 
Last Modified: 15-MAR-2000

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The information in this article applies to:

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

In a DLS (Distributed Link Service) environment where a "central" SNA Server has
distributed an 802.2 DLC (Data Link Control) link service configured for
MultiSap support, "remote" SNA Servers may have a problem activating multiple
connections through the distributed link service if all of the connections are
configured to use the same Local SAP.

CAUSE
=====

An 802.2 Data Link Control (DLC) link services can support up to 128 connections
over a particular Local SAP. The number of connections that can be configured
over using the same Local SAP will depend on the remote MAC/SAP addresses the
connections are configured to connect to.

When a DLC Link Service is initialized, DLC issues a DLC.OPEN.SAP command to
activate a SAP and reserve a number of link stations for that SAP. The DLC Link
Service is not designed to dynamically allocate additional link stations after
is SAP is opened, therefore it cannot allocate additional link stations if the
original allocation did not reserve enough to support all of the configured
connections for a particular SAP.

The problem described in the SYMPTOMS section can occur in a DLS environment
because the "Central" SNA Server that opens the SAPs for the distributed 802.2
DLC link service does not know how many connections will be using the link
service. If the original allocation of link stations is not sufficient to
support the number of connections that will be using a SAP, some of the
configured connections using that SAP will not activate and will stay in a
"Pending" state.

STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products listed at
the beginning of this article.

This problem was corrected in the latest SNA Server versions 3.0 and 4.0 U.S.
Service Packs. For information on obtaining these Service Packs, query on the
following word in the Microsoft Knowledge Base (without the spaces):

  S E R V P A C K


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

The hotfix modified the DLC Link Service so that it uses the DLC_REALLOCATE
command to dynamically allocate more link stations after the DLC.OPEN.SAP
command has been issued if they are needed. Another enhancement was made to the
DLC Link Service so that it no longer allocates a SAP buffer pool for every SAP
that is opened. By default, Windows NT DLC does not use SAP buffer pools. This
change saves a maximum of 64 KB of memory per opened SAP.

Note: The update DLC Link service has to be applied to the "Central" SNA Server.

Steps to Reproduce This Problem:

1. Have three SNA devices available to establish connections to (this can be any
  combination of Hosts, AS/400 or SNA Servers).

2. Set up a "Central" SNA Server site with one 802.2 DLC Link Service configured
  with the "Allowed to be distributed" option selected and the "Use Fixed SAP"
  option deselected.

3. Set up a "Remote" SNA Server site with one Distributed Link Service
  configured to use the link defined on the "Central" site in Step 2.

4. On the "Remote" site configure three connections using the same Local SAP on
  the same SnaRemX link service but to three different SNA devices (MAC
  addresses).

5. Activate the connections one at a time. The first two will go to an Active
  state and the last one will stay in a Pending state.

6. Stop one of the Active connections, and the Pending connection activate.

This can be reproduced the same way with two connections configured on the
"Remote" SNA Server and one local connection on the "Central" SNA Server.

Note: There may be cases when more than two connections using the same Local SAP
can be started before the next connection fails to activate. This will depend on
how the "Central" SNA Server is configured.

This problem does not occur if the distributed 802.2 link service is configured
with the "Use Fixed SAP" option enabled.

Additional query words:

======================================================================
Keywords          :  
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ400 kbSNAServ300SP1 kbSNAServ300SP2
Version           : WINDOWS:3.0,3.0 SP1,3.0 SP2,4.0
Issue type        : kbbug
Solution Type     : kbfix

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