Oracle Database 11gExpress Edition (Oracle Database XE) is an entry-level, small-footprint database based on the Oracle Database 11g Release 2 code base. It's free to develop, deploy, and distribute; fast to download; and simple to administer.
Get started with Oracle Database Express Edition 11g Release 2
Oracle Database XE is a great starter database for:
Developers working on PHP, Java, .NET, XML, 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
With Oracle Database XE, you can now develop and deploy applications with a powerful, proven, industry-leading infrastructure, and then upgrade when necessary without costly and complex migrations.
Oracle Database XE can be installed on any size host machine with any number of CPUs (one database per machine), but XE will store up to 11GB of user data, use up to 1GB of memory, and use one CPU on the host machine.