This background process is launched on demand, when you use the import historical data feature of Weather Station after choosing a ND-JSON file as source.
The process loads the file in the Weather Station database tables. After the process is correctly terminated, all data and indexes are available for use in historical charts and controls.
I do not recommend to try to use this data until the process is completely finished. Indeed, Weather Station caches are flushed only at the end of the operation, and before that, you could obtain or display erroneous values.
You can follow the progress of this process in the “At a glance” box of the Weather Station dashboard. Be warned that this progress can be a bit slow…
This process may take from minutes to hours. It has been optimized to not harm your database or your WordPress site. It does not interfere with the operation of your server and you are notified by email of the end of treatment.