The city and the stars

The City and the Stars is set a billion years in the future. The planet earth has long since become a desert wasteland, and humans (such as they are) now reside in a single, perfect, enclosed, and unchanging city named Diaspar. Gone and forgotten are such things as sexual reproduction, nuclear families, and scarcity. For the last many millions of years, the computer has instantly created all that's needed in the city. Humans are no longer born, but recreated by the computer, which stores the personalities of all people in a vast databank. When a new person is reborn, they are raised by a pair of guardians who volunteer to care for the child, and a tutor who is responsible for education. When that child reaches maturity, their old memories are gradually restored. People live this way for hundred of years at a time, then may pass several thousand in storage before being reborn again. This system has been maintained in a stable fashion for millions of years.