The RSS does not automatically delete data from the resource usage tables. You need to purge data you no longer need on a regular basis.
You can directly remove old resource usage data by submitting SQL statements. For example, use the following SQL statement to remove data more than seven days old from the ResUsageSpma table:
DELETE FROM ResUsageSpma WHERE TheDate < CURRENT_DATE - 7;
For more information about the DELETE syntax, see “Statement Syntax” in SQL Data Manipulation Language.