UniInt End User
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PI BASemAPI
ConstructionNote: If one or both of the cache files becomes invalid at any time during the construction process, the interface will disable the disconnected startup feature and continue to operate in the normal operation profile. During normal operation, a connection to the PI Server is required for the interface to start. This construction mode of operation is where the cache files are populated with the necessary digital state and point attribute data. Construction of the digital cache file is determined as follows. If the interface requires caching of the system digital state set, then all the system digital states will be retrieved from the PI Server and stored in the digital cache file. If the interface receives a digital point from the PI Server or queries the server for a digital point, all the digital states for the digital set associated with the PI point will be cached. Multiple points with the same digital state set will only require the complete digital set to be cached once. The point cache file is constructed in a similar fashion to the digital cache file. During interface startup, the interface requests and receives all points matching the required point source parameter listed in the startup command file. Upon receipt of the requested points from the PI Server, the point record along with the associated extended attributes are requested from the PI Server and immediately stored in the point cache file. The interface may request additional points such as event counters or trigger points. These points are cached as well. As a rule, any point requested by the interface will result in the point record and associated extended attributes being cached. The initial construction of the cache files will require additional startup time for the interface. When constructing the digital cache file, network latency may add to the startup time if the entire system digital set table is cached because an additional 1,024 network calls (one for each possible system digital state) will need to be executed because the interface is only capable of retrieving a single digital state from the PI API for a given call. PI points with large digital sets will also require additional caching time. The caching of the point record and extended attributes will add additional startup time to the interface as well. However, restarting the interface in a disconnected startup configuration with a fully constructed point cache file will eliminate all network calls and latency associated with communicating with the PI Server. This will dramatically reduce the interface startup time for subsequent interface restarts and allow the interface to collect data from the Data Source much quicker than without running in a disconnected startup configuration. The “Messages” section of this document contains a listing of typical messages sent to the pipc.log file during the construction mode. Download 1.93 Mb. Share with your friends:
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