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 like writing for cache ,what does that mean,which cache being writing rails cache or browers cache??