They are very distinct entities in an Oracle datacenter, as you shall see in the following
sections.
Databases
A database is a collection of data on disk in one or more files on a database server that collects
and maintains related information. The database consists of various physical and logical
structures, the table being the most important logical structure in the database. A table consists
O
Chapter 1: Getting Started with the Oracle Architecture 5
of rows and columns containing related data. At a minimum, a database must have at least tables
to store useful information. Figure 1-1 shows a sample table containing four rows and three
columns. The data in each row of the table is related: Each row contains information about a
particular employee in the company.
In addition, a database provides a level of security to prevent unauthorized access to the data.
Oracle Database 11g provides many mechanisms to facilitate the security necessary to keep
confidential data confidential. Oracle Security and access control are covered in more detail in
Chapter 9.
Files composing a database fall into two broad categories: database files and non-database
files. The distinction lies in what kind of data is stored in each. Database files contain data and
metadata; non-database files contain initialization parameters, logging information, and so forth.
Database files are critical to the ongoing operation of the database on a moment-by-moment
basis.
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