Apache Derby
Apache Derby (previously distributed as IBM Cloudscape) is a relational database management system (RDBMS) developed by the Apache Software Foundation that can be embedded in Java programs and used for online transaction processing. It has a 2.6 MB disk-space footprint.
Apache Derby is developed as an open source project under the Apache 2.0 license. Oracle distributes the same binaries under the name Java DB.
Derby technologies
Derby embedded database engine
The core of the technology, Derby's database engine, is a full-functioned relational embedded database-engine, supporting JDBC and SQL as programming APIs. It uses IBM DB2 SQL syntax.
Derby Network Server
The Derby network server increases the reach of the Derby database engine by providing traditional client server functionality. The network server allows clients to connect over TCP/IP using the standard DRDA protocol. The network server allows the Derby engine to support networked JDBC, ODBC/CLI, Perl and PHP.
Embedded Network Server