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From: pdg5001@yahoo.co.uk (Paul  Smith)
Newsgroups: comp.databases.oracle.misc
Subject: Basic  Oracle  Architecture  question
Date: 12 Dec 2002 15:31:16 -0800
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Hello,

I am new to Oracle and I am confused over a couple of basic
architecture issues.

(1) I have a multi-user application that connects to an Oracle
database. When I create Oracle users in DBA Studio, a schema is
created for each of the users. So user U1 is looking at a different
set of tables to user U2. But in my application I want each user of
the application to be looking at the same set of tables! What is the
usual way to handle this? Do I effectively have an "application"
Oracle user, so each user of my application connects to the database
as the same user (and therefore has the same permissions on the
databas objects)?

(2) What exactly is a Schema? I have two Oracle books, neither of
which explain whether it is a logical concept (which I'm sure it must
be), physical, or otherwise.

(3) I am aware that this question has been asked several times already
on Google, but unfortunately there are many conflicting answers (I am
hoping to get a categorical answer from a real expert out there!) - My
O'Reilly Oracle Essentials book states that "an instance can connect
to one and only one database" but Kyte's book tells me that "a
database may be mounted and opened by many instances. An instance may
mount and open a single database at any point in time." I guess these
statements are not necessarily contradictory. Assuming they are not
conotradictory, could someone tell me how an instance points to a
database, and how it can be changed to point to another database.

Many thanks,
Paul