Oracle GoldenGate is a data replication software for databases. It takes changes from a source database and replicates them to a target database. Oracle GoldenGate consists of the following processes:
The manager controls the other processes, including the start and stop functions.
The extract process pulls data out of a database and stores it either locally or remotely. If the extract process has to store the data locally, it does so by writing it to a file. If the extract process has to store the data remotely, it communicates with a remote server process and gets the server to store the data in files. The files that contain the data are called trails.
The server process is started automatically by the manager process, if a remote process contacts the manager to send data. Once the server process is started, communication takes place only between the sending extract process and the server process. The manager ceases to have any role in the communication between the sending extract process and the receiving server process. The server process takes the data from the sending extract process and stores it into a remote trail. Currently, there is no interface in the Oracle GoldenGate software to stop a server process. Hence, these processes must be killed manually.
A replicat process picks up the information from a trail and stores it into a target database. To achieve this, the replicat process must be able to make a local connection to the database.
A healthy Oracle GoldenGate instance has at least the manager up and running. Although such an instance is valid, it cannot process any data. A fully working Oracle GoldenGate instance has at least an extract process or a replicat process with the correspondig server up and running. You need at least two Oracle GoldenGate instances; one to serve as a sender and the other to serve as the receiver.
You can have different kinds of source and target databases. For example, you can have replication between MySQL and Oracle Database in either direction. The replication itself is always asynchronous. Synchronous replication is not possible using Oracle GoldenGate.