Residence Times and Retention Periods 
Residence Times and Retention Periods
The residence time is the minimum length of time that data must spend in the database before it meets the archivability criteria. Residence times can be set in application-specific Customizing.
The retention period is the entire time that data spends in the database before it is archived. The retention period cannot be set.
If the residence time is a month, data that has been in the system for two months will be archived. Data that is only three weeks old remains in the database.