UniInt End User
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PI BASemAPI
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- Hot Failover
- Input Data
- Interface Control Tags
Heartbeat PointThe heartbeat point is used to indicate that the interface is functioning. This point is updated once every failover update interval. If the interface is connected to the PI Server, the value of the heartbeat point will be incremented by UniInt from 1 – 15 and then wraps around to a value of 1 again. If the connection to the PI Server is lost, the value of the heartbeat point will be incremented from 17 – 31 and then wrap around to a value of 17 again. Once the connection to the PI Server is restored, the heartbeat values will revert back to the 1 – 15 range. During a normal shutdown process, the heartbeat value will be set to zero. Hot FailoverIn a hot failover configuration, the interface copy that is in a backup role collects and queues data in parallel to the interface that is in the primary role. The interface in the backup role does not send the data collected to PI. However, if a failover were to occur, the interface would immediately send its data to PI. This mode of failover eliminates loss of data for a single point of failure. Input DataThe term input data refers to data that originates on the data source and is collected by the interface and then written to the PI server. Interface Control PointsAn interface control point is a point on the data source that is used by UniInt to negotiate interface failover. The interface must be able to read the value of this point from the data source and write a value to this point on the data source. There are two types of interface control points: heartbeat points and active ID points. The value of these control points are echoed back to the PI Server. Interface Control TagsThe failover solution requires six interface control tags (PI tags). When UniInt starts and loads the list of PI tags, it will retrieve the information needed to be able to read from and write to the interface control points. If any of the six interface control tags are not found or fail to be loaded by the interface, the interface will log a message stating that the interface is not properly configured to participate in failover and then shutdown. Download 1.93 Mb. Share with your friends:
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