Today I test the new feature about "replication features" of PostgreSQL9.1, First I have installed the Hot-standby of PostgreSQL9.1 successfully. It is not a problem。 What I want to test is that I want to use commond "pg_ctl start promote " to active standby node instead of creating a trigger file 。 Yes, after I excute the commond, the standby node then becomes primary and allow write/read operations。 But the inital primary node can not switchover to the stnadby role automately. I am not usre If PostgreSQL9.1 is able to use "pg_ctl promote" do switchover between primary and standby node 。 Any body will explain this , thanks.
There is no 'demote' option for pg_ctl - if the primary was cold when the standby was promoted perhaps it could be converted to a standby manually, but otherwise it will need a new base backup from the new primary.
The normal reason for switchover would be if the primary has failed so this would not be necessary.