Autovacuum is enabled by default in PostgreSQL 9.0, and mostly does a great job of maintaining your PostgreSQL database. I say mostly because it doesn't know everything you do about the database, such as when would be the best time to perform maintenance actions.
Exercising control requires some thinking about what you actually want:
The first thing to do is to make sure autovacuum is switched on. You must have both the following parameters enabled in your