Hierarchical Parameters

As Plant SCADA supports clustering and the ability to run multiple servers of the same type on one machine, there are circumstances when the server component parameters (alarm, report, trend, I/O server) need to be tuned to a finer level than just machine level. For this reason, these parameters are hierarchical parameters that are capable of being implemented at a number of levels:

• Component type level

  The widest scope, the parameter value will apply to every instance of the server type.

• Cluster level

  The parameter value will apply to every instance of the server running in the specified cluster.

• Server level

  The parameter value will apply to the instance of the server running in the specified cluster, on the specified machine.

These parameters support hierarchical inheritance, that is, a parameter will:

• Apply a value set for it at a server level;

• If that is not specified, apply a value set for it at a cluster level;

• If that is not specified, apply a value set for it at a component level;

• If that is not specified, apply the default value for that parameter.

Example

The following Citect.ini file is applied to Server1 and Server2 (both in Cluster1), and to Server3 and Server4 (both in Cluster2).

[Alarm]SavePeriod = 500
[Alarm.Cluster1]SavePeriod = 600
[Alarm.Cluster1.Server1]SavePeriod = 1000

This is illustrated in the diagram below.

The values applied at each server for [Alarm]SavePeriod would be as follows:

Note: Hierarchical parameters may be set in the parameters database. In this case normal rules of precedence will apply. For more information see Parameter Precedence.

See Also

Configure Alarm Parameters for a Specific Cluster or Process