Now that we've fully explored the Oracle database architecture, a question might be raised. "Why make a distinction between the instance and the database at all? Don't they both operate on the same system?" By way of answer, yes; a vast majority of Oracle systems run on a single server. The background processes use a single set of CPUs and the caches run within a single set of memory chips. The database files exist on either storage that is within the machine or connected to it. Both the instance and database run on a single system. However, the Oracle RDBMS can be run in a different architecture—one in which the instance and database are physically independent.
Let's imagine an example for a moment. Let's say that we are DBAs for a small but growing company and we're responsible for the backend database that runs a customer billing system. We've chosen a small-sized server platform with two dual-core CPUs and 8 GB of RAM. This single machine connects...