Rules for two exporting stations

This example uses two remote stations (WestWing403 and EastWing403) to illustrate history policies.

You export histories from a source (usually a remote) station to a target (usually a Supervisor) station working under the source station’s Histories device extension of the NiagaraStation that represents this (local) station. Before exporting histories you need to set up one or more configuration rules in the target station for each source history. A configuration rule defines these properties:

• Two pattern properties identify the source station and its history names. These properties provide wildcards for selecting multiple stations and histories.

• The rule includes two properties: capacity and fullPolicy, which configure how the target station (usually the Supervisor) manages the histories.

Given the storage capacity of a Supervisor PC, a single, default rule may be all you need. If, for some reason, you are exporting histories to a remote controller station, you should definitely change the default configuration rule to specify smaller capacities. Even for a Supervisor station, you may need to change the default rule, and/or add additional optional configuration rules.

When a station exports a history, the target station uses the first matching rule to evaluate the data, and set up the capacity and full policy for the local (archived) history. The default rule is always at the top, and cannot be deleted or renamed. Other rules follow the default rule.

The Supervisor’s history policies configuration rules determine the capacity and full policy settings for each history at the time the station exports them from WestWing403 and EastWing403. Rules are matched to remote station (device) names and history names, which determine the corresponding capacity and full policy values to apply upon history creation. If a history does not match any rule, the system creates it using the capacity and full policy defined for the source history.