The Oracle Instance

The Oracle instance is defined as the shared global area (SGA) and the required background processes plus optional processes. The combination of the SGA, the background and optional processes is known as the Oracle instance. Each Oracle instance must have the following items.

• At least one datafile in the SYSTEM tablespace.
• A control file to maintain transaction control numbers and datafile information.
• Two redo log files to contain transaction redo information.
• A parameter file specifying constants initialising the Oracle system.