I've been having hours of fun, trying to work out why I couldn't map newly-created groups ( created in the File-Based Registry ) into BPM-specific roles, such as tw_authors which allows a user to log in and access Process Center and Process Designer.
In my case, I've created a set of temporary user accounts, and a corresponding group, in the File-Based Registry whilst I wait for "real" LDAP accounts to be created.
However, I couldn't work out why I couldn't see the newly created group ( IBM_Service ) when I attempted to add the group into the tw_authors role.
I faffed about ( that's English for trial and error ) for a while, before discovering the GroupCache option, as per the screenshot below and, even more importantly, the Reset link.
Once I reset the cache, the groups magically appeared.
Easy when one knows how :-)