OK, I found my original post on page 4. The question still applies. And no replies forthcoming.
Lightroom depends on the catalog in order to function. Deleting a catalog will not remove images from your hard drive. If you delete the catalog you delete the history of all the adjustments that you have made to your images using Lightroom. What you probably want to do is purchase an external hard drive and move images from your existing hard drive onto the new one. The easiest way to do this is to move them using Lightroom. But I don't believe you want to delete the catalog.
See my posted title: I backed up all 9000+ photos in 3 external hard drives. Two are full but the third still has a lot of capacity. All photos are saved in lossless .dng file. I don't have a problem going back to those external drive files if I want to do more post processing with the photos. I fail to understand why my startup disk on the Mac is full as the great majority of file space taken up are from LR5 photos. I only have two or three Mac Applications: Swift Publisher and Quicken Essentials, both of which do not require huge hard disk space.
By the way, those 9000+ RAW files are also stored in Pictures in the Mac. 9000 files each about 20Mb I calculate to 180Gb. Am I right?