Oracle is a complex, interrelated set of files and executables. With Oracle11g and Oracle12g it has not become any easier.
The database files include data segments, redo logs, rollback segments, control files, libraries, and system areas.
Each of these files is not a separate entity but is tightly linked to the components.
For instance, the data files are repositories for all table data.
The data file structure is controlled by the control file, implemented by the system areas, and maintained by a combination of the executables, redo, and rollback segments. Data files reference bfiles
that are tied to external procedures stored in libraries that are referenced in procedures stored in data files. This complexity leads to the requirement of a threefold backup recovery methodology to ensure that data recovery can be made. The next lesson describes the prerequisites to this course.