Following the preceding instructions Liferay Portal is run using an embeded database. While this is a good method to have it up and running fast for reviewing or developing, it has several drawbacks:
Only one user can access it at a time. This is because the data is stored on a file on disk and HSQL locks it when doing changes.
The data is stored inside the application server and might be lost on redeployment.
Fortunately Liferay has a great support for a good number of production-ready databases and it is easy to configure it to use them. The exact instructions will depend on the application server and database. Refer to the appropriate subsection of section 3.2 (Databases).