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[KB98]Producing internal variables on a station with redundancy

Tags: Multistation, Networking

Communication interfaces
14 years ago
By RM
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Applies to:

PcVue version 7.20c onwards.
While the basic content of this article remains valid, details may have changed since it was written.
Summary:

This article describes how to prevent sharing of internal variables between servers when you have defined single active server redundancy with internal variable switching.
Details:

When you define an association with a single active server, you must also configure the behaviour of internal variables. By default, only one station – the active server – produces the values of all the variables, both for the client stations and for the passive server. However if you set the option Without Internal Variables Switching, the internal variables are produced independently on each server.

Association_Creation_dialog_intnl_vars

Then neither the active nor passive server can distribute even those internal variables that are only of use on the servers. When switching of internal variables is enabled (i.e. the checkbox is unticked), all variables are produced by a single server. In either case, there is a limitation on servers producing their own variables.

Solution

Association of producer station

If each server needs to produce some internal variables, you can enable that as follows.

  1. Select the menu Configure/Communication/Networking stations to open the Networking Explorer.
  2. In the middle pane, right-click on Lists to select Add List then Add Servers List.
  3. In the Servers List Creation dialog, enter ALLSERVERS and click on OK.

Servers_List_Creation_dialog_AllServers

  1. In the Networking Explorer’s middle pane, right-click on ALLSERVERS and select Add a Station.
  2. In the dialog Add a Station, click on the first server’s name and select OK. Repeat that for the second server. Close the Networking Explorer.

You now have a list of the server stations that produce the variable whose values are to be distributed.

Networking_Explorer_AllServers_stations

Configuring a variable

You have to configure the variable so that it is only available to the servers.

  1. From the menu Configure/Variables/Selector, open the Variables Selector and double-click on the variable required.
  2. In its properties dialog, click on Advanced to open the Options dialog.

Variable_Advanced_Options_dialog_servers

  1. In Permanent Scan for Mimics, set the option Server Station.
  2. In Network Distribution, use the Servers drop-down box to select the ALLSERVERS list. Leave the Clients box empty.
  3. Click on OK, save the variable and close the Select Variables dialog.

The variable is now configured so as to be produced and consumed only by the servers in the ALLSERVERS list, here comprised of SERVER1 and SERVER2.

Note

You can apply this method to all internal variables that are to be produced by each of the stations (server or client) on the network.
  • Add the other networked stations to the list.

In this example, ALLSERVERS would then comprise SERVER1, SERVER2 and CLIENT3.

Created on: 22 Oct 2010 Last update: 13 May 2024