System Administrator’s Guide U42252-J-Z915-1-76

Introduction The Physical Database Structure
2.1 The Physical Database Structure
The physical database (see figure 1) consists of at least one control file, one
parameter file, at least two redolog files and at least one database file.
Figure 1: The physical database structure
●The database file(s) contain the data dictionary as well as the actual user
data (tables, indices, views etc.).
●The redolog files contain information on database recovery. They instantly
record any change made regarding the database. A database always
possesses at least two redolog files which are written cyclically.
●The control file(s) contain structural and management information.
●In the configuration file specifies the configuration of a database.
A database also possesses suitable programs (executables), which ensure its
functionality and form the Database Management System (DBMS).
2.2 The Logical Database Structure
At the logical level (see figure2), ORACLE only recognizes tablespaces (data-
base-specific, user-defined and temporary) consisting of at least one physical
database file. This tablespace structure also constitutes a backup unit for NSR-
ORA. The allocation between tablespaces and the corresponding files is per-
formed by NSR-ORA.
control file
configuration filedatabase file
redolog files