UniInt End User
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PI BASemAPI
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- Scan Class Input Device Scan Time
- Interface Disconnected Startup
Scan Class Scan TimeExDesc Keyword: [UI_SCINSCANTIME] Update Interval: At the completion of associated scan class. Description: The Scan Class Scan Time is the total amount of elapsed time in milliseconds to read data from the foreign device, populate the input tags, and then send the data to PI. The value for this tag is updated after each completed scan. Scan Class Input Device Scan TimeExDesc Keyword: [UI_SCINDEVSCANTIME] Update Interval: At the completion of associated scan class. Description: The Scan Class Device Scan Time is the time in milliseconds to read data from the foreign device and populate the input tags. The Scan Class Device Scan Time is a subset of the total Scan Class Scan Time and can be used to determine the percentage of time spent communicating to the foreign system compared with the percentage of time spent communicating with PI. If the Scan Class Skipped tag value is increasing, the Scan Time tags along with the Device Scan Time tags can be used to help identify where the delay is occurring – the foreign system communication, the PI system communication, or elsewhere in the interface controlloop. Interface Disconnected StartupInterfaces built with UniInt version 4.3.0.x or later include functionality to take advantage of the Disconnected Startup operation. Simply stated, disconnected startup allows the interface to start from a local cache file with or without a valid connection to the host PI Server. This critical functionality prevents data loss when an interface needs to start up and it does not have a connection to the PI server. In addition, even if a connection to the host PI server is available, if the interface is configured for disconnected startup, the interface will utilize the local cache to quickly get the interface started and collecting data from the Data Source. Using the disconnected startup feature when a PI server connection is available bypasses potentially long delays caused by the latency in network calls required to gather point information from the PI server, which in turn delays the ability of the interface to begin data collection from the Data Source. As an example, an interface with 50,000 associated PI points may take several minutes to retrieve all the PI points from the PI Server. Using the disconnected startup feature can reduce the interface time to load the same 50,000 PI points from the cache file to approximately 10 seconds. Results will vary depending on the system architecture and network latency. However, using disconnected startup will improve interface startup time, especially when large point counts are being used. The first time the interface is started with the disconnected startup parameter, a connection to the PI Server will be required to populate the cache files with the necessary data to support the disconnected startup feature on subsequent interface restarts. Two local cache files will be created on the interface node. The time to startup will be delayed while these files are being created. The local cache files contain the required PI Server version, PI point configuration, and Digital State information needed to start the interface. Once started, the interface can actively collect and buffer data retrieved from the Data Source when no connection to the host PI server is available. Download 1.93 Mb. Share with your friends:
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