As of now, RDS does allow changing configurations. So you can
- See the list of configurations that your RDS is using.
- You can change these parameters. I believe you can not change all
the parameters though. You can change those that are listed in the
RDS reference page.
As usual there are some static (or fixed) configuration parameters for which you have to restart you DB server and then there are dynamic options for which you dont need a restart.
Here is what the RDS reference manual says:
PostgreSQL parameters that you would set for a local PostgreSQL
instance in the postgresql.conf file are maintained in the DB
parameter group for your DB instance. If you create a DB instance
using the default parameter group, the parameter settings are in the
parameter group called default.postgres9.3.
When you create a DB instance, the parameters in the associated DB
parameter group are loaded. You can modify parameter values by
changing values in the parameter group. You can also change parameter
values, if you have the security privileges to do so, by using the
ALTER DATABASE, ALTER ROLE, and the SET commands. Note that you cannot
use the command line postgres command nor the env PGOPTIONS command
because you will have no access to the host.
Here is the official amazon RDS documentation for postgres: