Previous to this patch 2.0, players had a wdb file, that contained a cache of items/mobs/etc. In 2.0 Blizzard moved it. It should be in the new Cache folder, but mine wasnt. I manually added a WDB, then an enGB folder into the cache folder (Cache\WDB\enGB) and my framerate went up, my network traffic went down, and I got a bunch of cache files put into that folder by the wow client.
By creating a WDB folder inside your Cache folder, and then enGB folder (\World of Warcraft\Cache\WDB\enGB); your enGB folder will get populated with:
creaturecache.wdb
gameobjectcache.wdb
itemcache.wdb
itemnamecache.wdb
itemtextcache.wdb
npccache.wdb
pagetextcache.wdb
questcache.wdb
wowcache.wdb