A self-managing workload repository infrastructure (or "AWR" for Automatic workload repository) which is useful for a database server to collect and manage useful system performance statistics. The AWR runs automatically to collect performance data about the operation of the database system, and stores the data that it captures into the database. The collection process is done inside the database, and the collection process is highly efficient as data is retrieved directly from the shared memory of the database kernel. The data captured allows both system level and user level analysis to be performed without unduly impacting system performance, e.g., by eliminating or reducing the requirement to repeat the workload in order to diagnose problems. The AWR is configured to automatically capture snapshots of statistics data on a periodic basis as well as purge stale data on a periodic basis. The captured performance data includes one or more of the top N (e.g., 20 or 30) statistics for activities involving a large set of objects, time-based statistics, cumulative statistics, sampled data and metrics and other data types.