OS Image Cleanup Settings & deleting old images

OS Image Cleanup Settings & deleting old images

(I know this topic has been addressed before in  this thread from 9/2010, but since it's almost 2 years old and somewhat inconclusive, I'm going to address it again)

1) I'd like to clean off some older images/patches, but I want to make sure I don't delete anything inadvertently. I'm using WSM 4.0.1

Let's say I started with a base image, and have done 3 rounds of patching. My osimages directory would have the following files:

base_image
patch_01
patch_01.delta
patch_02
patch_02.delta
patch_03
patch_03.delta

(patch_03 is currently streaming to all clients)

Assuming I only want to keep the current image (Patch_03), and only want to be able to rollback to the previous version (patch_02), my understanding is:
-I can safely delete base_image, patch_01, patch_01.delta, and (I think) patch_02.delta
-I will be able to roll back from patch_03 to patch_02, but no further
-I can simply delete the unwanted files from the server directory

If anyone can confirm/correct these assumptions, I'd be most appreciative!

2) It seems that deleting the uneeded files from the server will not actually update the operating system hierarchy list (e.g., I'll still see base_image and patch_01, even if I trash the files). How do I get the operating system info page updated so that it's "in sync" with the files I've chosen to retain? I have tried setting the OS Image Cleanup preferences to delete every kind of file (all the check boxes are selected), have set the "Cleanup Interval" to 1 day, and have set "Recent Versions to Keep" to 2, but even though it's been a few days, I haven't seen any changes. Any guidance appreciated.