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If you find Oracle 10g fairly complex to install - if you find Oracle 10g memory hungry, especially when you’re trying to run several JVMs, and a VMWare instance in parallel with a heavy running Oracle 10g system. Think of Oracle Database 10g Express.

The installation of Oracle XE is straightforward and no necessary modifications of the Kernel params as Oracle 10g.

First install libaio :

# yum install libaio

Then download the Oracle XE rpm from Oracle.

Launch rpm install :

# rpm -ihv oracle-xe-10.2.0.1-1.0.i386.rpm

After install launch the following command as root, to configure HTTP Listener, SQL*Net Listener, SYSTEM & SYS passwords.

# /etc/init.d/oracle-xe configure

Oracle Database 10g Express Edition Configuration
-------------------------------------------------
This will configure on-boot properties of Oracle Database 10g Express
Edition.  The following questions will determine whether the database should
be starting upon system boot, the ports it will use, and the passwords that
will be used for database accounts.  Press <Enter> to accept the defaults.
Ctrl-C will abort.

Specify the HTTP port that will be used for Oracle Application Express [8080]:8888

Specify a port that will be used for the database listener [1521]:

Specify a password to be used for database accounts.  Note that the same
password will be used for SYS and SYSTEM.  Oracle recommends the use of
different passwords for each database account.  This can be done after
initial configuration:
Confirm the password:

Do you want Oracle Database 10g Express Edition to be started on boot (y/n) [y]:y

Starting Oracle Net Listener...Done
Configuring Database...Done
Starting Oracle Database 10g Express Edition Instance...Done
Installation Completed Successfully.
To access the Database Home Page go to "http://127.0.0.1:8888/apex"

The RPM/configure script does not configure environment. Add the following lines in your .profile file :

export ORACLE_HOME=/usr/lib/oracle/xe/app/oracle/product/10.2.0/server
export ORACLE_SID=XE
export PATH=$PATH:$ORACLE_HOME/bin

Try now a connection as system with SQL*Plus :

# sqlplus system/<password>

If you do heavy use of connection poolings, you could have problems with sessions/processes. Increase this params by connecting as SYSTEM , then launch SQL commands:

alter system set processes=200 scope=spfile;
alter system set sessions=225 scope=spfile;

More about Oracle XE:

Oracle XE is not only a database for novices, students, hobbyists, or small businesses; it can be used in many other situations.

It can bring value to DBAs, developers, analysts in their everyday job, regardless of the size of their businesses.

If you’re developer and you want to try DBA tasks, or you need a R&D database to try out new things it can be for you.

Oracle has built some limitations in the system:

First of all the memory : Oracle XE can not address more than 1GB memory.

Oracle XE can use only one CPU. This does not mean Oracle XE isn’t multi-tasks, but it cannot scale on multi processors machines, by using more than one CPU at a time.

One instance of Oracle XE per computer. It’s not really a limitation if you consider that we do not use one Oracle database per application : Oracle uses the concept of schemas to separate applications.

4GB limit on disk space. Even if it seems small, compared to multi terabytes of data warehouses, 4GB is already a huge amount for many applications.

Examples of uses :

The aggregation angle : you could consider to install Oracle XE instances on your users’s desktops, then schedule purges and refreshes of aggregated data (by push or pull). Advantages are : users can have control of their data, you reduce the load on your enterprise hardware, and you reduce the licenses costs for your Oracle database Enterprise Edition.

For the developer :

The configuration of Oracle XE is minimalist, so you can concentrate on the developments. Nevertheless, if you want to try DBA Tasks, you are in complete control.

The Admin control is a web GUI developed with Oracle Application Express(APEX, ex HTML Db) : you can create users with this admin tool, or if you prefer use Oracle SQL*Plus.

Oracle Express doesn’t support Java in the database (no internal JVM) : you can nevertheless connect an external JVM using JDBC.

The .NET CLR external process listener is included, so registered .NET programs can be called from database PL/SQL stored procedures. .NET support only exists on Windows version of Oracle XE.

Other development tools like Toad, SQL Developer, JDeveloper, Forms, PHP, Ruby are supported.

Oracle Database XE includes the Application Express Web-based development and deployment tool as well as XML DB. With the latter, you can immediately start using XML, WebDAV, and the built-in HTTP and FTP servers.

Finally, for people on Mac who are virtualizing guest OSes using Parallels, you have the opportunity to get an ASPLinux (based on Fedora Core) appliance, instrumented with Oracle Express 10g here.

More informations here