Note: If one or both of the cache files becomes invalid at any time during run-time, the application will disable the caching feature of the point caching 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 point data will be retrieved from the appropriate cache file and returned to the application. 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.
To keep the cache as up to date as possible while connected to the PI Server, the application should request point update information from the PI Server by calling pipt_signupforupdates. The application should then retrieve updates at regular intervals by calling pipt_updates. The API Cache Manager will process updates received and modify the point cache file if the pointsource of the update matches the pointsource in the SCacheConfig structure or if the PointId matches a previously cached point. The update will then be returned to the application for proper handling.
Note: Cache files are marked fully constructed or completely built by calling picm_setcachebuildcomplete. The user should mark the cache files as being complete by calling picm_setcachebuildcomplete once all the points necessary for the application are obtained.