What is Oracle databse structure?
Oracle database structure:  The relational model has three main aspects:
Structures: Structures are well-defined objects which store the data of a database. Structures and the data contained inside them can be manipulated through operations.
Operations: Operations are clearly described actions which permit users to manipulate the data and structures of a database. The operations on a database must adhere to a pre- described set of integrity rules.
Integrity Rule: Integrity rules are the laws in which govern those operations is permitted on the data and structures of a database. Integrity rules protect the data and the structures of a database.
An ORACLE database has both a physical and a logical structure. Through separating physical and  logical  database  structure,  the  physical  storage  of  data  could  be  managed  without affecting the access to logical storage structures.