Identify the processes and memory structures that make up an Oracle instance.
Components that make up an Oracle Instance
The diagram below illustrates the processes and memory structures that make up an Oracle instance. When you move your mouse over a box, you will see a brief description of what each particular process does.
The square boxes represent processes, while the circle in the center represents an area of memory that they all share.
Boxes drawn in bold are processes that are mandatory, and that will always be running when a database is open. The other processes are optional, and whether or not they will exist depends on the specific mix of Oracle features that you are using.
You will notice that several of the process names end with one or more zeros. DBW0 is one example. An Oracle instance can be configured to have several such processes running simultaneously.
For example, if your database experiences a high volume of updates,, you might configure the instance to run with two database writers, which would be named DBW0 and DBW1. This generally only makes sense when you have multiple CPUs to run those processes.
The procedures for displaying a list of running processes are different, and depend on whether you are using