How oracle process a select in a multi-threaded server

The client connection will send a request to the dispatcher. The dispatcher will first place this request onto the request queue in the SGA
(1). The first available shared server will dequeue this request
(2) and process it. When the shared server completes,
the response (return codes, data, and so on) is placed into the response queue
(3) and subsequently picked up by the dispatcher
(4), and transmitted back to the client.