[[_database]] == Relational Database Setup {{book.project.name}} comes with its own embedded Java-based relational database called H2. This is the default database that {{book.project.name}} will use to persist data and really only exists so that you can run the authentication server out of the box. We highly recommend that you replace it with a more production ready external database. The H2 database is not very viable in high concurrency situations and should not be used in a cluster either. The purpose of this chapter is to show you how to connect {{book.project.name}} to a more mature database. {{book.project.name}} uses two layered technologies to persist its relational data. The bottom layered technology is JDBC. JDBC is a Java API that is used to connect to a RDBMS. There are different JDBC drivers per database type that are provided by your database vendor. This chapter discusses how to configure {{book.project.name}} to use one of these vendor-specific drivers. The top layered technology for persistence is Hibernate JPA. This is a object to relational mapping API that maps Java Objects to relational data. Most deployments of {{book.project.name}} will never have to touch the configuration aspects of Hibernate, but we will discuss how that is done if you run into that rare circumstance. NOTE: Datasource configuration is covered much more thoroughly within the link:{{book.appserver.datasource.link}}[the datasource configuration chapter] of the {{book.appserver.admindoc.name}}.