August 2005
Intermediate to advanced
154 pages
4h 48m
English
Content preview from Oracle DBA Pocket Guide
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Oracle Architecture
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Oracle Architecture
This section provides a brief overview of the architecture of
Oracle Database 10g and Oracle9i Database.
Database Versus Instance
For most Oracle users, the terms database and instance are
used synonymously. However, there are differences that
become especially important if you are running in Oracle’s
parallel environment: Real Application Clusters (or RAC, for-
merly known as Oracle Parallel Server, or OPS). Simply put,
the database is the data on disk, stored in operating system
files (or possibly, under Unix, in raw files), while the instance
is composed of system memory and the background pro-
cesses. The instance is STARTed using Oracle Enterprise Man-
ager (OEM) or SQL*Plus. The database is then MOUNTed by
the instance and is finally OPENed. The users CONNECT to
the instance in order to access the data in the database.
Figure 1 shows the basic components of the Oracle database
and instance.
Except in a parallel environment, there is a one-to-one corre-
spondence between instance and database. In the parallel
world, the database can be MOUNTed by multiple instances.
Background Processes
The background processes reside in memory, are executed by
the processor(s), and are responsible for the proper opera-
tion of the database. Depending on the options configured,
there may be from 6 to 35 (or even more) background pro-
cesses. Each background process has a
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.