June 2001
Intermediate to advanced
384 pages
11h 36m
English
book
Oracle Essentials: Oracle9i, Oracle8i and Oracle8, Second Edition
by Rick Greenwald, Robert Stackowiak, Jonathan Stern
Content preview from Oracle Essentials: Oracle9i, Oracle8i and Oracle8, Second Edition
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Chapter 2. Oracle Architecture
This chapter focuses on the concepts and structures at the core of the Oracle database. When you understand the architecture of the Oracle server, you’ll have a context for analyzing the rest of thefeatures of Oracle.
Instances and Databases
Many Oracle practitioners use the terms “instance” and “database” interchangeably. In fact, an instance and a database are different (but related) entities. This distinction is important because it provides insight into Oracle’s architecture.
In Oracle, the term database refers to the physical storage of information, and the term instance refers to the software executing on the server that provides access to the information in the database. The instance runs on the computer or server; the database is stored on the disks attached to the server. Figure 2-1 illustrates this relationship.
Figure 2-1. An instance and a database
The database is physical: it consists of files stored on disks. The instance is logical: it consists of in-memory structures and processes on the server. An instance can connect to one and only one database. Instances are temporal, but databases, with proper maintenance, last forever.
Users do not directly access the information in an Oracle database. Instead, they pass requests for information to an Oracle instance.
The real world provides a useful analogy for instances and databases. An instance ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.