By default, the system logs activities into temporary files and batch-processes them periodically. But depend on which version you are on, the process is little different.
In V8.1 and V8.2, there is a setting in web.config for the interval which you can adjust.
https://docs.kentico.com/display/K82/Enabling+activity+tracking
In V8, that settings key wasn't available, but there is something else
https://docs.kentico.com/display/K8/Enabling+activity+tracking