As the number of users within the grid increases, it becomes harder to maintain an accurate list of who should be authorised to use a dCache instance. Instead of trying to keep track of who is a member of a VO, the solution is to allow an external component, a VOMS server, to state that a user is a member of a VO.

When faced with a request (e.g., store a file, read a file) from a user, dCache can be configured to trust the VOMS server and authorise requests based on the user's VO membership.