FIM DB Sizing Calculator
FIM has two databases (well three if we count the FIM Certificate Management service): FIMService FIMSynchronizationService Here is a calculator in excel that you can download and use to calculate how big to make your databases. In my experience the FIMService database size depends mostly on how many request objects are in the database. The FIM Sync Database depends mostly on how much run history details (step object details) you generate and keep.