Based on the FIM DB Sizing calculator, these 2 values control the eventual size of the databases:
- Request Retention in Days
- Days of Run History Kept
Where can I change these values?
are these registry keys?
There isn't any magic way to control the number of days run history kept within the Synchronization service, however you can schedule a powershell script to be run regularly that will clear out run log entries before a particular date -> see: http://social.technet.microsoft.com/wiki/contents/articles/2096.how-to-use-powershell-to-delete-the-run-history-based-on-a-specific-date-en-us.aspx
From memory Microsoft recommend keeping the run history to under 14 days or less than 10,000 entries (which ever results in the lower number of entries).
In terms of the request retention that is something configurable within the FIM Portal (I don't have access to an environment to tell you exactly where though).
Edit: see this post for the Portal configuration -> http://social.technet.microsoft.com/Forums/en-US/ilm2/thread/043e37a9-2383-44ed-9369-830a4ecf8111/