The recommended configuration steps are:

•Create expiration rules that satisfy the customer needs.

•Create partitions and assign the appropriate expiration rule.

•Each folder that needs maintenance must be connected to a partition that has an expiration rule

•Properly configure the cleanup in Back4 regards the Purge days (the default is 365 days which is not the best settings in a live environment)

It's not necessary to do anything special to avoid deleting the content that is still assigned to "something", because in this case the deleting will fail.