Principles of operation

The PI OPC Alarms and Events (OPCAE) interface is designed to retrieve alarming data from an OPC compliant Alarm and Events Server and store the data in the PI Data Archive.

This section describes operation of the interface, including the storage of event attributes, handling of time stamps, making/breaking connections, and OPC advising.

At startup the interface attempts a connection to the OPC AE server. If the server will not start, the interface will perform retries every 5 seconds. The Interface Status Utility can be used to monitor the connections between the server and the interface. Upon connection the interface will check the status of the OPC AE server: RUNNING, FAILED, NOCONFIG, SUSPENDED and TEST. The server time is also retrieved and will be compared to the PI time to compute a bias for the timestamps associated with PI archived events.

Tags to be advised are then added to the interface and are specific to the event type configured: Simple, Tracking or Condition. When the interface starts, optional Quality/Severity tags are built to store the quality/severity attribute(s) of events when the ExDesc field contains the directive for these optional tags. If these tags already exist, no action is taken. Optional quality/severity tags are only built for conditional event tags. If the ExDesc is edited for the parent tag and one or both directives are removed, the tags will not be deleted and the interface will write Scan Off for those tags. If the parent tag is deleted the interface will write Scan-Off also.