Clusters

Clustering allows you to group different sets of the runtime components within a single project, allowing multiple independent systems to be monitored and controlled. Many Plant SCADA items require a cluster to be specified in order for them to work correctly.

There are countless variations in how a clustered system can be configured. An appropriate configuration will depend on the requirements for the solution to be deployed and the environment in which it is being deployed. For more information and examples, see Typical System Scenarios.

Rules of Clustering

When configuring Plant SCADA the following clustering rules apply:

• Each cluster needs to have a unique name.

• Each server process needs to have a unique name.

• Each server process needs to belong to one cluster.

• Each cluster can contain only one pair of redundant alarm servers. They need to reside on different machines.

• Each cluster can contain only one pair of redundant reports servers. They need to reside on different machines.

• Each cluster can contain only one pair of redundant trends servers. They need to reside on different machines.

• Each cluster can contain an unlimited number of I/O servers.

  

The next diagram demonstrates circumstances where clustering is not configured correctly.

The Plant SCADA compiler or the Runtime Manager detects when the rules of clustering are not being observed and advises the user accordingly.

Cluster Context

The Cluster Name can either be explicitly specified when the item is called or displayed, or an item can use the default cluster context of the calling process or page.

If your system has only one cluster, you do not need to specify a cluster.Plant SCADA will allow tags or tag references without a cluster context specified to be automatically resolved if every tag name in the project is unique.

This means if you use a unique naming convention for your tags, you will be able to configure a multi-clustered system without having to specify cluster context. For any tags that are not unique, #COM will be displayed if cluster context cannot be determined.

Note: This capability is enabled by default via the parameter [General]TagDB.

See Also

Assigning Graphics Page Objects to a Cluster at Runtime