Java is one of the core languages (SQL, PL/SQL, Java, XML, and HTML) that are tightly integrated in the Oracle Database suite of products. The Extensible Markup Language (XML) is a hierarchical data structure that describes data by embedding the metadata with the data structure. Java has become the primary language for new applications that are written for Oracle databases. Why does an Oracle DBA care about Java? Java in an Oracle environment impacts architectural decisions, performance, leveraging new technologies, security, and application development. Java-stored procedures can run in the Oracle database server. So, if Java code can run in the Oracle database server, then DBAs are going to have to deal with related Java issues. Also, DBAs that can support the middle tier (application server, Web Services, J2EE, Oracle Net Services, and so on) in n-tiered environments as well as application development (Java, XML, HTML, and others) will increase their value to an organization. Java knowledge is important in all tiers of an Oracle Database architectural environment. However, with Java playing such a key role in so many technology areas in Oracle Database, the key features and functionality introduced in this section are important for DBAs to understand.