Oracle Database 10g contains two major components:
1. The physical database and
2. The Oracle instance.
The physical database consists of the files that physically reside on the system, such as datafiles, redo log files, and control files.
The Oracle instance is made up of a large memory area and a set of background processes. The instance provides a means for users to connect to the database to retrieve, add, delete, and modify data.
Some Other Components:
a. Oracle Executables and Library Files
Oracle executables and library files are not considered part of the database.
b. Multiple Instances
Each database will usually have only a single instance, but on some platforms, the DBA can configure multiple instances of a single database.
