SymmetricDS

SymmetricDS is web-enabled, database independent, data synchronization/replication software. It uses web and database technologies to replicate tables between relational databases in near real time. The software was designed to scale for a large number of databases, work across low-bandwidth connections, and withstand periods of network outage.
By using database triggers, SymmetricDS guarantees that data changes are captured and atomicity is preserved. Support for database vendors is provided through a Database Dialect layer, with implementations for MySQL, Oracle, SQL Server, PostgreSQL, DB2, Firebird, HSQLDB, H2, and Apache Derby included.
Synchronization can be configured to push data (trickle-back) or pull data (trickle-poll) at an interval. SymmetricDS allows for 2-tier and even n-tier synchronization, such as the following:

• A farm of web server nodes fronting an enterprise-class general office database
• A handful of regional servers for synchronizing from the general office to remote geographical areas
• 1000(s) of store server nodes using a departmental class database to sync with a regional node
• 10(s) of Point of Sale (POS) register nodes using an embedded database to sync with a store server

Deployment options include the following:

• Web application archive (WAR) deployed to an application server such as Tomcat, Jetty, or JBoss
• Standalone service
• Embedded in an application

SymmetricDS is written in Java and licensed as open source software under the GNU Lesser General Public License (LGPL).