Active-active (also called Master-Master or Bi-Directional) replication captures data changes from two or more systems and replicat the changes to synchronize the data. Active-Active replication is often needed for high availability, load balancing and scaling out purposes.
Oracle GoldenGate is known to be one of the first and the best replication tool handling active-active replications. As of Oracle GoldenGate 12c, it provides (Refer to Oracle GoldenGate 12.1.2 Documentation - Configuring Oracle GoldenGate for Active-Active High Availability for more information) the followings:
Oracle GoldenGate supports active-active configurations for DB2 on z/OS, LUW, and IBM i, MySQL, Oracle, SQL/MX,SQL Server, and Sybase. However, the setup is different from database to database. In this example, I will show you how to setup an active-active data replication between two MySQL database instances. The example setup is about setting up an active-active replication between MySQL 5.5 and MySQL 5.6 instances.