Delete Statistics Records
The server deletes statistics records based on the value specified for the statistics initialization parameter stat.max.age.
The stat.max.age parameter controls the amount of time that the server retains the statistics record in the database. When statistics records reach the value specified by the stat.max.age parameter, the server automatically deletes them. To retain all of your records, back up your database regularly or set stat.max.age= to disable automatic deletion.