How does VistA work

This page decribes the basic CPRS/VistA model. This will not be much more than a picture.

-FT

This isn't a picture, but generally,

1. CPRS runs on a person's own computer.

1. CPRS uses a part of a person's own computer called the RPC Client.

1. The RPC Client uses the computer's network software and hardware to establish a link to some bigger computer running the VistA server. The part of the VistA server that the RPC Client connects to is called the RPC Broker.

1. The RPC Broker sets up a part of the VistA server to handle any questions and answers that are needed by the original person's CPRS session. This could be called the user's RPC proxy.

1. CPRS on the person's PC uses the RPC client to send requests to the VistA server, which replies with answers.
   1. An example request might be "I am this person, authorize me."
   2. The RPC proxy then uses the access code and verify code which was sent with the request, and tries to authorize that person's CPRS.
      1. If it succeeds, then other requests can be answered by the proxy.
      2. If it does not succeed, then the proxy waits for a proper authorized user.

1. Eventually, the person using CPRS finishes with their work, and the RPC proxy on the VistA server doesn't get any requests for a while. The VistA server then removes the proxy and the connection is broken.