Confused about the default schema

Question

Hi,
I am a little bit confused about the schema concept.
I want to create a new schema called APP and then create several users and roles based on the schema APP. The default schema for the users should be APP achema.
How can I make the schema APP the default schema for the new users that I am creating?
I feel that there are some schema design concepts that I have to learn. Is there any resource on the internet that I can read and learn more about oracle schema design best practices?
Any help would be appreciated,
Ali

Answer 1

A schema holds object definitions, and in the case of table & index objects the schema also holds the data.
A user owns the schema.
Therefore the user 'owns the definitions (including any functions, procedures, sequences, tabels, etc.)
Other users may be granted access to some, or all, of the objects in a schema. This is done through the 'GRANT ...' command. For example, consider the following steps:
1) create user app_owner
2) create table object test owned by the app_owwner
3) create user app_user
4) grant select, update, insert and delete on app_owner's test table to app_user
5) add synonyms to avoid needing to qualify the table's schema name.
done as follows:
oracle@fuzzy:~> sqlplus system
SQL*Plus: Release 10.2.0.1.0 - Production on Mon Apr 3 20:07:32 2006
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Enter password:
Connected to:
Oracle Database 10g Express Edition Release 10.2.0.1.0 - Production
Create the app owner userid. Note there is no need to ever log in to that user, even to create tables.
SQL> create user app_owner
  2  identified by xyz
  3  account lock
  4  quota unlimited on users
  5  default tablespace users
  6  temporary tablespace temp;
User created.
Creating objects in a schema can be done by providing the schema name, or by switching schema in newer versions of Oracle
SQL> create table app_owner.test ( t number );
Table created.
Create a userid that will access the table. Set that userid up to access the database and (for future) give it the capability to create it's own synonyms
SQL> create user app_user
  2  identified by xyz
  3  temporary tablespace temp;
User created.
SQL> grant create session to app_user;
Grant succeeded.
SQL> grant create synonym to app_user;
Grant succeeded.
Now give the user access to the objects
SQL> grant select, update, insert, delete on app_owner.test to app_user;
Grant succeeded.
Let's test it out. Insert by qualifying the schema name on the object, then create a synonym to avoid using schema, and try it all using the synonym
SQL> connect app_user/xyz
Connected.
SQL> insert into app_owner.test values (4);
1 row created.
SQL> create synonym test for app_owner.test;
Synonym created.
SQL> insert into test values (3);
1 row created.
SQL> select * from test;
         T
         4
         3
SQL>  Note that some people want to use PUBLIC grants and PUBLIC synonyms. This is a real bad idea if you want to ensure long term security of the data and want to host several different applications in the same Oracle instance.
This, and a whole lot more, is in the 'Concepts' manual for your version of the database at http://docs.oracle.com