Converting a SAM-FS Filesystem to un-shared

I'm going to convert my filesystem from shared to UN-shared.  The man page says I should be able to do this:

samfsck -F -U samsf1

My question -- will this actually run a full samfsck repair (potentially taking hours) or will it only do what's necessary to convert the FS?  Appx. how long should I plan to have my filesystem offline to perform this action?

Thanks!