XE, the free database, Oracle

Now almost a year ago that Oracle offers a free version of its database, with the main objective of introducing the 'Oracle World' to developers, DBAs, students and trainers, and hardware and software vendors that want to distribute with their a product database without license fees. 
The product is Oracle 10g Express Edition (Oracle Database XE), and obviously has its limitations. You can only use 1 processor server that is installed, up to 1 GB of RAM, and storage is limited to 4 gigabytes of user data. When you exceed these limitations, Oracle offers a simple upgrade process to other more complete versions, and where do you have to pay licensing. 

Anyway is a very valid option for those who want to practice with Oracle database, or for those who need a database limited in size, but reliable and efficient, and free. 
With the database, including Oracle Application Express, an intuitive environment that allows gráficamentes perform the basic tasks of administration of the database. 
You can download this database, or look for more specific information on the same Oracle Database XE 
I recommend checking the installation of the Oracle Database XE Datasheet, and features of Oracle Application Express