H2 is a relational database management system written in Java. It can be embedded in Java applications or run in the client-server mode. The disk footprint is about 1 MB.
The software is available as open source software under the Mozilla Public License or the Eclipse Public License.
The main feature of H2 are:
Very fast, free for everybody, source code is included
Embedded, server and cluster modes
JDBC and ODBC API; browser based Console application
Written in Java; can be compiled with GCJ and IKVM.NET
Small footprint: around 1 MB
H2 Database Engine Version 1.0.78 (2008-08-28)