Hi,
if you look at our knowledge base, you’ll find the data definition schema:
https://slimstat.freshdesk.com/support/solutions/articles/5000650210-what-is-the-table-schema-used-to-store-all-the-information-
All the data is stored in qkdce_slim_stats, while qkdce_slim_stats_3 can be deleted as it is a leftover of previous versions of the plugin. Please note that Slimstat also supports a feature that allows you to ARCHIVE page views older than a certain date (in a separate table qkdce_slim_stats_archive), which you could then periodically download and empty in the database.
Slimstat also allows you to use a SEPARATE DATABASE to store all the information it collects, if that can help mitigate your issues.
Best,
Jason