help caching rails

Hai All
I have a problem. can help me plz…

problem:
I want cache 1 varible…
ex:
user1 request to server… my program make 1 variable… if first time variable will generate(find to table). after generate I want that variable is cached.
user2 request to server… because user1 has requested, so that variable not generate again. but read form cache…
user3 request to server… —> same with user2. (variable form cache)

can help me plzzzz…

Thank you…