Hot Standby
From PostgreSQL Wiki
Hot Standby is the name for the capability to run queries on a database that is currently performing archive recovery. Log Shipping replication allows you to create one or more standby nodes that are replicas of the primary node (or master node). Standby nodes can then be used for read-only query access.
Hot Standby is being developed for inclusion in PostgreSQL 8.5 by Simon Riggs of 2ndQuadrant via public sponsorship.
The feature is now committed to CVS and is included in PostgreSQL 8.5 Alpha3. There are about 7 pages of docs here: Hot Standby docs
This feature will augment the capabilities of streaming replication that have also been discussed for inclusion in r8.5, though does not rely on it and has minimal interaction with it.
Questions, Issues, Bugs
If you have a Question, an Issue or wish to report a Bug then you are welcome to do that via pgsql-bugs@postgresql.org or pgsql-hackers@postgresql.org, though please also copy simon@2ndQuadrant.com on those mails.
Diagnosing problems
There are sometimes reasons why you cannot connect. Check the log for messages.
First, check that you are connected to the correct server and that the server is in recovery. You can check this by looking at "ps" output and looking for a "startup process". If you can't find one, you aren't in recovery.
If you can connect, check you are in recovery by running SELECT pg_is_in_recovery();
If you think you should be able to see an object or some data, check that the standby has processed all outstanding WAL. It may just be the standby is lagging behind.
Look at the current snapshot using "select txid_current_snapshot();". Look at pg_locks and pg_stat_activity.
