The enterprise information systems (EIS) tier consists of database servers, enterprise resource planning systems, and other legacy data sources, like mainframes. These resources typically are located on a separate machine than the Java EE server, and are accessed by components on the business tier.
The following Java EE technologies are used to access the EIS tier in Java EE applications:
The Java Database Connectivity API (JDBC)
The Java Persistence API
The Java EE Connector Architecture
The Java Transaction API (JTA)