The parameter file is the main location that's used for defining parameter values for the PostgreSQL server. All the parameters can be set in the parameter file, which is known as postgresql.conf. There are also two other parameter files: pg_hba.conf and pg_ident.conf. Both of these relate to connections and security, so we'll cover them in the appropriate chapters that follow.
Before we start this recipe, we need to locate postgresql.conf, as described in Finding the current configuration settings recipe.
Some of the parameters take effect only when the server is first started. A typical example might be shared_buffers, which defines the size of the shared memory cache. Many of the parameters can be changed while the server is still running.
After changing the required parameters, we issue a reload command to the server, forcing PostgreSQL to re-read the postgresql.conf file (and all other configuration files). There are a number of ways...