I'm just beginning to learn the product so i hope i am clear and don't butcher the terminology..

The previous engineer backed up a whole bunch of data for a particular subclient (file system data). It looks like the data was backed up under a storage policy set to infinite retention. This consumed a number of tapes which i'd like to free up and return to the scratch pool. What is the proper way to do this?

I assumed I should create a new storage policy with 7 day retention (the backup I want to delete is from February), reassign the backup set to this new policy, and then what.. wait? Shouldn't that make CV purge the data and free the tapes? Or will it still hang onto the last full for some reason?

Anyways appreciate any help purging data and freeing up tapes.. I'm not really clear how thats done.

Assigning a subclient to a new SP will only result in future backups being assigned the new retention period....the existing data will stay the same.

You can delete jobs by highlighting the Storage Policy, right clicking on the copy (in the right hand pane) and selecting view ---> jobs.

Find the job you want to prune (delete), right click on it and select 'prune job'.

If you want to clear a full tape then you can do the above but, select 'media' instead of 'jobs' and select 'delete contents'...this will then move the tape to the scratch pool.

You could also simply change the retention on the existing storage policy and then run data aging.  It will prune off all data past the new retention setting.