PostgreSQL arrives configured for use on a shared system, though many people want to run dedicated database systems. The PostgreSQL project wishes to ensure that PostgreSQL will play nicely with other server software, and will not assume that it has access to the full server resources. If you, as the system administrator, know that there is no other important server software running on this system, then you can crank up the values much higher.
Before we start, we need to know two sets of information:
We need to know the size of the physical RAM that will be dedicated to PostgreSQL
We need to know something about the types of applications for which we will use PostgreSQL