- Conceptual Mode: Conceptual mode, also known as pattern, is a description of the global data base structure in the database, and is the public view of the whole user. This description is abstract, does not involve specific hardware environments and platforms, and is not related to a software environment.
- external mode: External mode is also called sub-mode or user mode, he is the database user can see and use the local data logical structure and characteristics of the description, is the database user's data View, is with a certain The logical representation of the applied data. The outer mode is usually a subset of the pattern. A pattern can have multiple external modes.
- Internal mode: Also known as storage mode, one mode has only one internal mode. He is a description of the physical structure and storage of data, defining the many internal record types, the organization of indexes and files, and the details of data control.
Oracle Getting Started database system architecture----Level Three mode
