how do i clear rails cache

hii all,
         i would like to know how do i clear rails cache memory,Actully
in my
rails application i havt to upload and download large size file,so when
i am trying to downlaod files multiplt time
am getting failed to allocate memory...
is there any way to cleas rails cache memory through code...

one more thing when i am downloading files from browser,i got a message
writing for cache ,what does that mean,which cache being writing
rails cache or browers cache??