The Retention Periods tab on the Edit Jobs view displays retention information for all jobs and the tables associated with those jobs. A retention period is the number of days a table retains its data before that data is purged.
The Weekly Job purges data that exceeds the retention limits set for each table. Data is purged from a table on a First-In-First-Out basis.
The Cleanup Schedule in the Monitored Systems portlet allows you to schedule table cleanup to occur after Performance Data Collection daily jobs have completed successfully. This makes sure the data is archived to the Performance Data Collection database before the cleanup occurs.