UniInt End User

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UniInt Interface User Manual
PI BASemAPI

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• /host
• /host=PrimaryPI

PI Tag	Value
Description
Active ID Input Tag Exdesc: [UFO_ACTIVEID]	Updated by the redundant Interfaces Values range between 0 and the highest of the Interface Failover IDs (typically 2)	The Active ID Input Tag must be configured as a valid input PI tag for the interface and it must be configured to read the Active ID point on the data source. Consult the Interface User’s manual for a description of configuring input tags. The exdesc must start with the case sensitive string: [UFO_ACTIVEID]
Active ID Output Tag Exdesc: [UFO_ACTIVEID]	Updated by the redundant Interfaces Values range between 0 and the highest of the Interface Failover IDs (typically 2)	The Active ID Output Tag must be configured as a valid output PI tag for the interface and it must be configured to write to the Active ID point on the data source. Consult the Interface User’s manual for a description of configuring output tags. The exdesc must start with the case sensitive string: [UFO_ACTIVEID]
Heartbeat 1 Input Tag Exdesc: [UFO_HEARTBEAT:1]	Updated by the Interface on IF-Node1 Values range between 0 and 31	The Heartbeat 1 Input Tag must be configured as a valid input PI tag for the interface and it must be configured to read the Heartbeat 1 Point on the Data Source. Consult the Interface User’s manual for a description of configuring input tags. The exdesc must start with the case sensitive string: [UFO_HEARTBEAT:1] The value following the colon (:) must be the Failover ID for the interface running on IF-Node1. In this example, the Failover ID is 1.
Heartbeat 1 Output Tag Exdesc: [UFO_HEARTBEAT:1]	Updated by the Interface on IF-Node1 Values range between 0 and 31	The Heartbeat 1 Output Tag must be configured as a valid output PI tag for the interface and it must be configured to write to the Heartbeat 1 Point on the Data Source. Consult the Interface User’s manual for a description of configuring output tags. The exdesc must start with the case sensitive string: [UFO_HEARTBEAT:1] The value following the colon (:) must be the Failover ID for the interface running on IF-Node1. In this example, the Failover ID is 1.
Heartbeat 2 Input Tag Exdesc: [UFO_HEARTBEAT:2]	Updated by the Interface on IF-Node2 Values range between 0 and 31	The Heartbeat 2 Input Tag must be configured as a valid input PI tag for the interface and it must be configured to read the Heartbeat 2 Point on the Data Source. Consult the Interface User’s manual for a description of configuring input tags. The exdesc must start with the case sensitive string: [UFO_HEARTBEAT:2] The value following the colon (:) must be the Failover ID for the interface running on IF-Node2. In this example, the Failover ID is 2.
Heartbeat 2 Output Tag Exdesc: [UFO_HEARTBEAT:2]	Updated by the Interface on IF-Node2 Values range between 0 and 31	The Heartbeat 2 Output Tag must be configured as a valid output PI tag for the interface and it must be configured to write to the Heartbeat 2 Point on the Data Source. Consult the Interface User’s manual for a description of configuring output tags. The exdesc must start with the case sensitive string: [UFO_HEARTBEAT:2] The value following the colon (:) must be the Failover ID for the interface running on IF-Node2. In this example, the Failover ID is 2.
State 1 Tag Exdesc: [UFO_STATE:1]	Normally updated by the Interface on IF-Node1. May be updated by the interface on IF-Node2 if IF-Node1 is unable to update the tag Values range between 0 and 5, see description.	The failover state tags are optional and do not require a point on the Data Source. The value of the state tag can be written to the Data Source by configuring a normal interface output tag and setting the SourceTag attribute to the failover state tag. The failover state tags were designed to be digital tag assigned to a digital state set with the value values. 0 = Off: The interface has been shut down. 1 = Backup No Data Source: The interface is running but is unable to communicate to the data source. 2 = Backup No PI Connection: The interface is running and connected to the data source but has lost its communication to the PI server. 3 = Backup: The interface is running and collecting data normally and is ready to take over as primary if the other copy shuts down or experiences problems. 4 = Transition: The interface will be in this state for only a short period of time. The transition period is designed to prevent thrashing where both copies attempt to assume the role of the primary interface. 5 = Primary: The interface is running, collecting data and sending the data to PI.
State 2 Tag Exdesc: [UFO_STATE:2]	Normally updated by the Interface on IF-Node2. May be updated by the interface on IF-Node1 if IF-Node2 is unable to update the tag Values range between 0 and 5, see description of State 1 tag.	The failover state tags are optional and do not require a point on the Data Source. The value of the state tag can be written to the Data Source by configuring a normal interface output tag and setting the SourceTag attribute to the failover state tag.

The redundant solution requires two separate interface nodes communicating with the data source. The failover scheme requires the creation of six tags on the PI Server and three control points on the data source that are specifically used for controlling failover operation. The PI tags are necessary to initialize the interface with configuration information for reading and writing to the control points on the data source. Once the interface is configured and running, the ability to read or write to the PI tags is not required for the proper operation of failover. This leads to a solution that does not require a connection to the PI server after initial startup in order for failover to operate since only the control points on the data source are monitored. However, values are echoed to the PI Server for the user to monitor. Manual failover can be accomplished by manually changing the active ID point on the data source to the appropriate failover ID.
The figure above shows a typical network setup in the normal or steady state. This by no means includes the myriad of configurations that are supported, it is meant to be used for an example. If the hardware configuration differs from the figure, the settings for the two redundant interfaces will remain the same with the exception of the /host startup parameter. If the interfaces are communicating to a stand-alone PI server, the /host parameter for both interfaces must be the same.
In order to ensure outputs to the datasource continue when a PI server in the collective becomes unavailable, the interface running on IF-Node1 will need the /host parameter set to a PI server that is part of the collective, and the interface running on IF-Node2 will need the /host parameter set to a different PI server that is part of the collective. The continued operation of outputs in the face of a PI server becoming unavailable assumes the source data for output data (data that is read from PI and written to the data source) comes into PI from a process that sends values to all of the PI servers in the collective via n-way buffering.
The solid red line in the figure shows input data flow when the interface on IF-Node1 is in the primary state. The data is read from the data source by the interface and sent to buffering. Buffering sends the input data to all of the PI servers in the collective via n-way buffering.
The solid blue line shows output data flow. Since the interface on IF-Node1 is configured with /host=PrimaryPI, the interface signs up for exceptions with the PI server on PrimaryPI. Exceptions are received by the interface and sent to the data source via the interface.
The dashed red line shows input data flow to the backup interface. The dashed line stops at the interface because the interface does not send the data to buffering unless the interface is in the primary state. If the backup interface were to transition to the primary state for any reason, the interface would send the input data to buffering. Buffering would then write the data to all of the PI servers in the collective via n-way buffering.
The dashed blue line shows output data flow to the backup interface. The dashed line stops at the interface because the interface does not send the data to the data source unless the interface is in the primary state. If the backup interface were to transition to the primary state for any reason, the interface would send the output data to the data source.
In the event the Primary PI server becomes unavailable for any reason, the primary interface informs the backup interface that it has lost its connection to the PI server. The backup interface will transition to the primary state because its status is better than the current primary interface. If for example the entire Business Network were to go off line so that both copies of the interface lost their connection to their respective PI servers. The primary interface would remain primary because the backup interface’s current status is the same, not better. In this case output data would no longer flow to the data source because there is no way for any of the interfaces to get the exception data.

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