Extractors exist for reading information from the following sources:
Reading the MySQL binary log (binlog) directly from the disk and translating that content and session information into the THL. Using this method to read the binlog in it's different formats, such as the statement, row and mixed-based logging.
Remotely from MySQL server over a network, including reading from an Amazon RDS MySQL instance. This enables the replicator to read the information remotely, either on services where direct access to the binlog is not available, or where we cannot be installed.
Directly from Oracle up to Oracle 11g using the Oracle CDC system. The Change Data Capture solution within Oracle makes it possible to extract information from the tables within Oracle, although it's availability is limited and implies some overhead on the Oracle service, it can provide a flexible solution for extracting row-based information.
Directly from Oracle by reading the Oracle redo and supplemental logs. This solutions reads the logs directly in a similar fashion to extracting the information from the MySQL binary log. Unlike CDC, this method is very fast and efficient and provides an ideal solution for reading data including some data types not supported by the CDC solution.
Offboard reading from the Oracle redo and supplemental logs. This similar to the basic supplemental log solution, but rather than requiring the replicator directly on the Oracle host, the reading can be done with a smaller redo log extractor, or even remotely on an NFS or other network file system solution. This is a much more practical solution for deployments where the original Oracle host is unable to support the replicator (for example, due to operating system limitations), or where the source Oracle system is not allowed to execute third-party solution for security or performance reasons.