The Tiger skin is based on a simple - client side - database which makes it possible for the skin to reach out for any photo in the album. This is used in Search or the Tag cloud box.
The skin is optimized for quick page loads, therefore at the beginning only the current folder and the top level database are loaded. The rest is loaded only when it's needed, e.g. the visitor starts a search.
Tag cloud box needs the whole database right at the beginning, so if you have a very large album - > 10 - 20 000 photos - you might want to turn Tag cloud box off in order the page can load quickly.
Note, in order the databases don't get corrupted you have to allow jAlbum to process all the subfolders (Settings / Advanced / Process subdirectories need to be ON, Process only updated subdirectories, OFF). Also you will have to update tree.json and deep-data.json with every Upload. Take care if you're uploading manually. jAlbum's "Upload" function will manage them.