Let's say I've got a Master server (Server A) and a Standby server (Server B), with streaming replication under PostgreSQL 9.2.x. One day, Server A goes down. So I promote Server B, and users are able to add / change data on Server B.

After a few days, Server A has been repaired, but obviously the data on Server A is out-of-date by a few days. What are my options to update Server A? Do I have to replicate the entire cluster from Server B? It can't be as simple as setting Server A as a Standby off Server B, can it?