As we mentioned before, the Oracle instance is composed of the necessary processes and memory structures required to operate the Oracle kernel. The instance is the first thing invoked when the database is started.
The first components of the Oracle instance that we will examine are the Oracle background processes. These processes run in the background of the operating system and are not interacted with directly. Each process is highly specialized and has a specific function in the overall operation of the Oracle kernel. While these processes accomplish the same functions regardless of the host operating system, their implementation is significantly different. On Unix-based systems, owing to Unix's multiprocess architecture, each Oracle process runs as a separate operating system process. Thus, we can actually see the processes themselves from within the operating system.
For instance, we can use the ps
command on Linux...