Oracle Database 10g Express
Edition (Oracle Database XE) is an entry-level, small-footprint
database based on the Oracle Database 10g Release 2 code base
that's free to develop, deploy, and distribute; fast to download;
and simple to administer. Oracle Database XE is a great starter
database for: Developers working on PHP, Java, .NET, and Open
Source applications; DBAs who need a free, starter database for
training and deployment; Independent Software Vendors (ISVs) and
hardware vendors who want a starter database to distribute free
of charge. Educational institutions and students who need a free
database for their curriculum. Oracle Database XE can be installed
on any size host machine with any number of CPUs, but this free
version will only: store up to 4GB of user data, use up to 1GB
of memory, and use one CPU on the host machine.