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Appendix F: Microsoft SNA Server v2.11


Note: Screen snapshots are copyright Microsoft Corporation


This document provides sample views of an 802.2 DLC connection for Microsoft SNA Server for Windows 95/NT. We have validated the CCIAPPC component against Microsoft SNA Server version 2.11. This document is arranged in a logical sequence for a new installation of the SNA Server product.

F.1 Installing DLC for Windows NT or '95

Microsoft SNA Server requires the Microsoft 32-bit DLC protocol to provide support for a connection over 802.2. You should already have installed the 32-bit DLC driver for Windows '95 or Windows NT. If you have not yet done this, please follow the instructions for installing this driver in Configuring DLC over 802.2 on Windows 95 or Configuring DLC over 802.2 on Windows NT.

F.2 Installing Microsoft SNA Server

You should have already installed Microsoft SNA Server. In addition you should have specified the MS DLC in the SNA Server Setup program.

F.3 Configuring Microsoft SNA Server

After successfully installing the SNA Server product, you can start to configure your APPC connection. You should have a VTAM definition of the connection you are attempting to configure available to you during the configuration.

From the Microsoft SNA Server(Common) program folder, start the SNA Admin program.

F.4 Step 1: Configuring the Local Server

Select New Server from the Services menu. This will display the Server Properties dialog box.

  1. Enter a Server Name which will be used to identify this local MS SNA Server, for example, this could be the machine name.
  2. Enter the Network Name for this SNA network. This should be obtained from the network administrator of the host system.
  3. Enter the Control Point (CP) name assigned to this machine. This should be obtained from the network administrator of the host system. The CP Name should match the Physical Unit (PU) name assigned to this machine as specified in the PU definition in VTAM for this machine.

F.5 Step 2: Configuring the Adapter

Now configure the Adapter by clicking on the Adapters button in the Server Properties dialog box. This will display the Adapter Properties dialog box.

  1. Select the Service Name SnaDlc1 which is the MS 32 Bit DLC installed previously.
  2. Select the correct adapter type (in this case Token Ring or Ethernet) which is being used by this machine. If the machine has more than one adapter then choose the adapter type which was configured for use with MS DLC.

Complete the Local Server configuration by clicking on the Close button.

F.6 Step 3: Configuring the Connection

  1. Select the local Server in the Servers and Connections window which you have just configured in Steps 1 and 2 above.
  2. In the Services menu choose New Connection which then displays the Insert Connection dialog box.
  3. Select the type of connection, in this case 802.2.
  4. Choose OK at which point the Connection Properties dialog box will appear.
  5. Fill in the Connection Name with a name up to 8 characters long which will describe the connection, e.g. the destination of the connection.
  6. Select the Link Service SnaDlc1, this is the protocol which will be used to access the network adapter.
  7. For the Remote End select Host System.
  8. Set the Allowed Directions to both Incoming and Outgoing.
  9. Set the Activation to By Administrator initially. This can be changed to On Demand or At Server Startup later when we are sure that the connection is configured correctly.

F.7 Step 4: Configuring the Connection Setup

Now display the 802.2 Setup dialog box by clicking on the Setup button in the Connection Properties dialog box.

  1. Enter the 12 digit hexadecimal Remote Network Address of the network controller attached to the remote host system. This should be obtained from the network administrator of the host system.
  2. Enter the 8 digit hexadecimal Local Node ID which is used to identify this local system on the SNA network. The first 3 digits is the block (IDBLK) number followed by the last 5 digits of the node (IDNUM) number. These numbers must correspond with the IDBLK and IDNUM fields of the PU definition for this machine as defined in VTAM on the host system.

At this point you must check with the network administrator of the host system to see whether the host system uses Format 3 type XIDs.

Also check with the network administrator of the host system whether the Node Id of the host system should be configured.

Now set the connection retry parameters by clicking on the Retry Timers button.

  1. Set a value for the Maximum Number of attempts that SNA Server will make to establish the connection with the host system. The possible values range from 1 to Unlimited. We suggest a value of 2.
  2. Set a value for the Delay after failed attempts. This is a value in seconds between each attempt. The range is from 5 to 255 seconds, with a default of 10.

Now check the Advanced settings for the 802.2 connection by clicking the Advanced button.

The Advanced settings contains parameters which in most cases can be left to their default values. Two which may need modification are the BTU Length and the XID Type.

  1. Specify a value for the maximum BTU Length based on the following formula. BTU = MAXDATA - 9, where MAXDATA is the value of the MAXDATA parameter of the PU definition for this machine. NOTE: For a 4 Mbs Token Ring specify a BTU value of 4195 or less. For a 16 Mbs Token Ring specify a value of 16393 or less. For an Ethernet LAN specify a BTU value of 1493 or less.
  2. The XID Type should reflect the type used by the host system. Format 0 only sends the local Node ID and is used only when hosts do not support the default Format 3 XID. Format 3 sends up to 100 bytes of identification data which includes the local Node ID and the Control Point name. Independent APPC LUs must use format 3 XIDs. The default is Format 3.

To complete the configuration of the connection click on the OK button.

Before attempting to communicate using CCIAPPC you must define the local and remote LUs which will be used to communicate over the SNA connection you have configured. In this section we will describe the configuration of Independent LUs to be used to communicate over the host connection. When communicating with Host systems running VTAM (or NCP) the Remote LU is known as the APPLID (pronounced 'apple-id').

F.8 Step 5: Configuring Local LUs

  1. In the Servers and Connections window, select the SNA Server name and then in the Services menu select Assign LUs and when the Insert LU dialog box appears select OK.
  2. For the LU Alias specify the LU name as defined in the list of LUs defined for this PU in VTAM on the host system. At this point this name is automatically duplicated for the LU Name.
  3. Enter the Network Name which should be the same as the Network Name field of the SNA Network Control Point in the Server Properties dialog box (activated by double-clicking on the SNA Server name in the Servers and Connections dialog box). The Network Name and LU Name together form the Fully Qualified LU Name.
  4. If you want to automatically associate this Local LU with every Remote LU configured in SNA Server then select the Enable Automatic Partnering check box.
  5. Select the check box marked Member of Default Outgoing Local APPC LU Pool.

To complete the configuration of the Local LU click on the OK button.

F.9 Step 6: Configuring Remote LUs

Unlike Local LUs, Remote LUs are assigned to a connection which will be used to communicate with it.

  1. In the Servers and Connections windows, select the connection configured in Steps 3 and 4, then in the Services menu select Assign LUs. When the Insert LU dialog box appears select APPC (Remote) and then OK.
  2. Enter the LU Alias, at which point this name is automatically duplicated for the LU Name. Enter the Network Name. These should match the definition of the LU as it exists on the remote system, in this case in the form of a VTAM APPL definition on the host system.
  3. Select the Supports Parallel Sessions check box.

F.10 Step 7: Partnering LUs

The partnering of a Local LU with a Remote LU forms a relationship between these LUs which will enable us to establish a session for CCIAPPC to communicate over.

  1. In the Servers and Connections windows, on the right hand side of the window, double-click on the Local LU which you have created.
  2. In the APPC LU Properties dialog box select the Partners button.
  3. In the LU 6.2 Partner LUs dialog box select the Add... button.
  4. In the Add APPC LU Partner dialog box select the partner LU (in this case it will be a previously defined Remote LU) and the mode for the LU-LU pair. A number of default modes are defined already, for example #INTER, which is adequate in most cases of LU 6.2 intercommunication. However if you need a customized mode see the section entitled Defining a Mode below.
  5. Click on the Close button.

F.11 Configuring Session Limits: Defining a Mode

A Mode is used to define the attributes of sessions used between a Local LU and a Remote LU.

If the default mode #INTER is not appropriate (because its settings are incompatible with the modes defined on the host system for the Remote LU, or perhaps because a larger number of sessions is required) then a new mode can be defined.

CCIAPPC uses a single APPC session for each CCI session between the client and the server (e.g. between the MFA client and Fileshare running on a mainframe). When CCIAPPC establishes a connection between the client and server the attributes of the Mode determine, amongst other things, the number of CCI sessions available between the Local LU and the Remote LU (APPLID in VTAM). Hence the Mode determines how many client sessions can be established using the same Local LU - Remote LU pairing.

The Parallel Session Limit and the Minimum Contention Winner Limit together determine how many sessions can be established by the Local LU (see below).

For example: if 10 client sessions are required, all using the same Local LU then the Mode session attributes might be:

Parallel Session Limit = 20
Minimum Contention Winner Limit = 15
Partner Minimum Contention Winner Limit = 0

Alternatively the same number of client sessions could be attained by using multiple Local LUs with the client sessions divided between these LUs.


IMPORTANT NOTE: When a connection is established between a Local LU and a Remote LU the Mode characteristics are negotiated. This means that it is possible that the partner system (e.g. mainframe) will reduce the session limits to values which it can support. This may mean that fewer client sessions than expected will be supported. Hence it is important that the Mode characteristics, as defined for both the Local and Remote LUs, are compatible.


F.11.1 To Define a New Mode

  1. In the Servers and Connections windows, on the right hand side of the window, double-click on the Local LU which you have created.
  2. In the APPC LU Properties dialog box select the Partners button.
  3. In the LU 6.2 Partner LUs dialog box select the Modes... button.
  4. Enter Mode Name, this should match the Mode Name as defined on the Host system in VTAM. This can be the default log mode specified by the DLOGMOD parameter of the VTAM Applid (APPL) definition.
  5. Enter the Parallel Session Limit. This is the maximum number of sessions that can be established between the two LUs.
  6. Enter the Minimum Contention Winner Limit. This is the number of sessions that the Local LU can establish without needing the permission of the Remote LU.
  7. Enter the Partner Min Contention Winner Limit. This is the number of sessions that the Remote LU can establish without needing the permission of the Local LU. Note that the sum of the Minimum and Partner Min Contention Winner Limits must be less than or equal to the Parallel Session Limit. If you are in doubt over these values check with the network administrator of the host system.
  8. Do not select Enable Automatic Partnering.
  9. Select High Priority Mode.
  10. Enter the Pacing Send Count and Pacing Receive Count. These values should be obtained from the system administrator of the host system.
  11. Enter the Max Send RU size and Max Receive RU size. These values should be obtained from the system administrator of the host system.
  12. Select Close to complete the Mode definition. The new Mode should appear in the Modes pull-down window when choosing a mode for a Local LU - Remote LU partnership.

Repeat this section until all required Modes have been added.

Refer to the section entitled Configuring Modes for LU-LU Pairs in chapter 6, Configuring LUs for APPC of Part 2 of the Microsoft SNA Server Administration Guide for more information.

F.12 Step 8: Enabling CCIAPPC to Find the Local LU

It is very important that the CCIAPPC module be able to determine the Local LU to use for communication with the Host application. You may have configured everything else correctly and all of your other APPC applications may work, but if you miss this final step you will fail to establish a CCI session with the host application. If the CCI-INITCLIENT call returns CCI error 9 and CCI_GETERROR returns the message "CCIAPPC failed to allocate an APPC session, ensure that Local LU is defined" it is likely that you have failed to complete this final step. When CCIAPPC attempts to allocate an LU 6.2 session with the remote system it must specify the Remote LU name which it requires a session with. This is the Remote LU name specified in the CCI Servername parameter (e.g. the /S parameter in FHREDIR.CFG). However, APPC needs to know the Local LU name as well as the Remote LU name when attempting to establish a session between the LUs.

The manner in which it determines the Local LU name in SNA Server is by one of two mechanisms as described below:

  1. Configure the Local LU to be a member of the Default Outgoing Pool.

    When we configured the Local LU above, we selected the check box marked Member of Default Outgoing Local APPC LU Pool in the APPC LU Properties dialog box. This means that when CCIAPPC attempts to allocate a session with the Remote LU it will examine the Local LU partners configured with the Remote LU and select one which is a member of the Default Outgoing Pool. However, if there are multiple Local LU partners configured with the Remote LU which are members of the Default Outgoing Pool then any of these Local LUs could be selected. If this side-effect is undesirable then implement the following method.

  2. Configure a default Local APPC LU Alias on per user or group basis.

Now go to the File menu and select Save Configuration. It is not necessary to restart the SNA Server service to activate the new configuration. For further information concerning assigning default LUs to users and groups see the section entitled Assigning Default APPC LUs to Users or Groups in chapter 6, Configuring LUs for APPC, in the Microsoft SNA Server Administration Guide.

F.13 Step 9: Configuring a 3270 LU for the 3270 Applet

In order to use the SNA Server 3270 Applet for 3270 terminal access to the host system a 3270 LU must be configured for use by each terminal session.

  1. In the Servers and Connections window select the host connection which is to be used for the 3270 terminal session
  2. In the Services menu select menu item Assign LUs...
  3. In the Insert LU dialog box select 3270 and then click on the OK button
  4. In the New 3270 LU Properties dialog box:

Repeat Step 9 until you have configured all the 3270 LUs which you require for 3270 terminal sessions.

F.14 Step 10: Associating a 3270 LU with a User

When a user runs the SNA Server 3270 Applet a 3270 LU is required in order to establish a session with the host system. This 3270 LU may come from a pool of 3270 LUs or may be associated with the user. We will describe the latter case, associating a 3270 LU with a user.

  1. If the user has not yet been configured in SNA Server:
  2. In the Users and Groups window select the user with whom you want to associate a 3270 LU.
  3. In the Users menu select the Assign LUs menu item.
  4. In the Assign User LU/Pool Sessions dialog box select the required 3270 LU (configured in Step 9 above) from the list of Available LUs and Pools.
  5. Click the OK button.

Now go to the File menu and select Save Configuration. It is not necessary to restart the SNA Server service to activate the new configuration.

When the specified user starts the SNA Server 3270 Applet a session will be established using the 3270 LU associated with the user.

F.15 Step 11: Activating the Configuration

Once the settings described above have been made the configuration must be saved before stopping and restarting the SNA Server service.

  1. In the File menu and select Save Configuration.
  2. In the Servers and Connections window select the server and in the Services menu select Stop Service.
  3. Once the server status has gone to Inactive, in the Services menu select Start Service, the service should then go to Active status.

Once the service is active the underlying connections will activate if the Activation type was defined as On Server Startup or On Demand.

Connections configured for Incoming and Outgoing calls go to On Demand/Incoming status when successfully activated. The connection will go to active status when the first session is established or if activated manually by the administrator.

F.16 Error Reporting and Diagnostics


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