My cfw is 6.60 nightly

So should i enable or disable umd cache,because if i do these i don't know what gappen after that

Sorry my english is bad

*So should i enable or disable umd cache?,because if i do these i don't know what happen after that.

Depends on what you want to do. If you do not use "Force High Memory Layout"< and you dont use plugins like atpro (pro Online) or other plugins that use the kernel memory range - then you can (or even should) leave UMD Cache (If you're playing from an UMD) and ISO Cache (If you're playing from a .iso image file) on. If you want to use atrpo and other plugins that use kernel memory - you need to disable both UMD and ISO Cache.