Operational overview for UniInt interfaces

Interfaces connect data sources to the PI System by connecting to the data source, collecting data, and then sending it to Data Archive. Interfaces can be configured to run as services, use failover, limit user access, increase data security, monitor interface performance and status, use disconnected startup, and in some cases, write data back to the data source.

Interface operation uses the following processes:

1. Startup

2. Connection to Data Archive

3. Data collection

4. Point updates

5. Shutdown

Startup

At startup, the interface connects to Data Archive. If the Data Archive node is unavailable, the interface continuously attempts to connect. If the interface cannot connect to Data Archive and disconnected startup is not enabled, the interface cannot collect data.

Connection to Data Archive

For interfaces to connect to Data Archive, PI trusts must be enabled. See the PI Data Archive security topic in the PI Universal Interface (UniInt) user guide for information on that process.

Data collection

For interfaces where disconnected startup is enabled, the interface loads PI points from a locally-cached subset of the Data Archive point database, and starts collecting data whether or not it is connected to Data Archive.

For interfaces where disconnected startup is not enabled, the interface connects to Data Archive, loads the PI points, and starts collecting data. Time-series data is collected and sent to Data Archive for each successfully loaded point.

Point updates

After starting and loading the PI points, the interface checks and updates point attributes for points that have been added, changed, or deleted.

Shutdown

The UniInt exit handler will perform an orderly shutdown with the following operations:

6. Write Intf Shut system digital state to all health points for the interface.

7. Write stop status information to failover points or interfaces configured with UniInt failover, when the interface is the last running instance of the failover pair.

8. Clean up the interface.

9. Update scan-based and event-based input points with the specified digital state for interfaces with a configured shutdown status,

10. Update the I/O rate point and reset the I/O rate counter to zero for interfaces with an associated I/O rate.

11. Disconnect from Data Archive.