Configure alarms in a client/server topology

The client/server topology separates nodes that serve data (Application Object Server nodes) and the clients that consume data (visualization nodes). There more clients than servers.

A platform object must be deployed on each client and each server. One or more of the platforms on the Application Object Server should be set as an alarm provider and each alarm consumer should query one of the Application Object Server platforms directly. This deployment minimizes the network traffic by channeling the alarm traffic to specific alarm providers.

If the platforms on the visualization node(s) are set as alarm providers, each of those platforms requests all alarms continuously, loading the network with unnecessary traffic. While a platform can be configured to subscribe only to alarms of particular areas, the platform still requests the alarms for the configured areas on a continual basis.

By configuring the Application Object Server platforms as alarm providers, only one node requests alarm updates. The visualization node(s) only request alarms when a window containing the alarm display is active. Alarm consumers only request the alarms that are required to satisfy the alarm query.

As stated previously, each platform is capable of providing all alarms in the galaxy. However, if all of the consumers are using a single platform as the sole alarm provider in the galaxy, there is a single point of failure for all alarm consumers. Also, the single platform would constantly be receiving the alarms from all of the other Application Object Servers, which would cause a heavy traffic load on the network.

If your client/server architecture consists of more than one Application Object Server node, take the following measures to ensure the highest availability of alarm information to the alarm consumers:

1. Configure the alarm consumer queries to query each Application Object Server platform for the areas that are hosted on that platform.

2. Configure the Application Object Server platform alarm providers to provide only alarms for the areas hosted by that platform.

These two configurations lower network traffic between Application Object Servers due to alarm distribution and ensure that no one Application Object Server is a single point of failure for alarm delivery to the consumers on the visualization nodes.

Best Practice

The following list summarizes the key points for setting up an optimized alarm distribution system in a client/server architecture. The list also applies to a widely-distributed SCADA system environment:

• The platforms on the visualization nodes should not be alarm providers.

• The alarm consumers on the visualization nodes should query each Application Object Server individually for the areas hosted by that platform.

• The Application Object Server Platform Alarm Providers should be configured to only be providers for the Areas that are hosted by that Platform.