UniInt End User
Download 1.93 Mb.
|
PI BASemAPI
- Navigate this page:
- Synchronization
UtilizationNote: If one or both of the cache files becomes invalid at any time during run-time, the interface will disable the caching feature of the disconnected startup configuration and continue to operate in the normal non-caching operating profile. During normal operation, a connection to the PI Server is required to retrieve point update information. The utilization mode is the run-time use of the caching files that have been validated and fully constructed. In this mode, all requests for digital state or point attribute data will be routed to and managed by the API Cache Manager. Requested data will be retrieved from the appropriate cache file and returned to the interface. While the cache files are in a fully configured and valid state, no network calls will be made to the PI Server to retrieve the requested information. The utilization process using fully configured cache files allow the following run-time operations without requiring a connection to the PI Server. Validate cache files to be used for interface instance. Retrieve PI Server version information. Retrieve event counter point configuration. Retrieve system digital state set if requested. Retrieve point configuration for points matching interface point source value. This includes retrieving the digital state set for digital points. Retrieve additional points required by interface. (Trigger, Source, etc.) The interface will request point update information from the PI Server at regular intervals. The API Cache Manager will process updates received and modify the point cache file if necessary to keep the cache files up to date. The update(s) will then be returned to the interface for proper handling. SynchronizationDuring interface disconnected startup with fully configured cache files, only the cache files will be used to configure the interface with the necessary data to begin data collection. If the interface has been disconnected from the PI Server, the point configuration data stored in the cache files may no longer match what is currently on the PI Server. Point attribute changes may have been made or points matching the interface point source may have been added or deleted. Therefore, a synchronization mechanism is required to make sure the PI point configuration data running on the interface is up to date. The synchronization mode keeps the caching files up to date and passes any changes in point configuration to the interface for processing. The synchronization process can only begin after the interface has been successfully started using the disconnected startup configuration, entered its control loop, and established a connection to the PI Server. Once these conditions are satisfied, the UniInt Cache Manager will request the API Cache Manager to retrieve a list a PI points matching the interface point source from the PI Server. If a point received from the PI Server does not exist in the point cache, it will be added to the cache and then a point create update will be sent to the interface. If a point has been modified as indicated by the “changedate” attribute, the cache will be updated with the correct attribute information and a point edit update will be sent to the interface. A comparison of the points found on the server is made to what currently exists in the caching files. If a point is found in the cache file that no longer exists on the PI Server, a point delete update will be sent to the interface. The optional /CacheSynch startup parameter, described in the Startup Command File Configuration section, specifies whether cache synchronization is enabled and the time period allocated to synchronization. By default, synchronization of the cache files is enabled and the time period allocated for synchronizing the cache is set to a default of 250 milliseconds (ms) per synchronization attempt. This means one iteration through the interface control loop can use a maximum of 250ms to synchronize as many points as it can. The synchronization process will continue in this manner until all the points have been synchronized. Once the cache files have been synchronized, cache synching will be disabled unless there is an interruption with the connection with the PI Server. If the PI Server becomes disconnected for any reason, point synchronization will be restarted upon reconnection to the PI Server. The “Messages” section of this document contains a listing of typical messages sent to the pipc.log file during the synchronization mode Download 1.93 Mb. Share with your friends:
|