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PI BASemAPI
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- Output Data
- Thrashing
Interface CopyThe term interface copy refers to a single interface executable that is participating in a failover configuration. Interface InstanceAn interface instance is defined as an interface with a unique set of PI tags determined by PointSource and interface ID (/id startup parameter). An interface instance may be redundant or standalone. When discussing a failover configuration, the interface instance includes both redundant copies of the interface since they have the same PointSource and interface ID. Output DataThe term output data refers to data that originates in PI or the failover copy of the interface itself, and written to the data source. Primary InterfaceWhen an interface is installed in a failover configuration, only one copy will be actively sending data from the data source to PI and from PI to the data source. This copy of the interface is referred to as the primary interface. PointFor the discussion concerning failover, an entity that exists on the data source is referred to as a point. A point may also be referred to as a control point. TagFor the discussion concerning failover, an entity that exists on the PI Server is referred to as a tag or PI tag. A tag may also be referred to as a control tag. ThrashingThrashing is defined as two interfaces continually alternating between the primary and backup roles. This condition must never be allowed to occur. A defective implementation of failover can lead thrashing. Warm FailoverIn a warm failover configuration, the backup interface does not actively collect data. The backup interface is able to load the list of PI tags and is in a state ready to start collecting data as soon as the primary interface fails or stops collecting data for any reason. If the backup interface assumes the role of primary, it will start data collection and it will send its data to PI. There may be some data disruption. Download 1.93 Mb. Share with your friends:
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