Changed data management

Oracle GoldenGate 12c offers a number of changed data management options. These are:

• Integrated capture and delivery
• Classic mode
• Coordinated mode
• DDL replication

Integrated capture and delivery

Integrated capture has been available since Oracle GoldenGate 11g Release 2, which inherited many features of the Oracle Streams product that is a part of the Oracle database. The feature is fully supported against Oracle database 11.2.0.4 version and above.

The integrated architecture enables GoldenGate to manage the capture and delivery of the changed data more efficiently and enable compatibility with other Oracle database products, such as RAC, RMAN, and Data Guard.

The integrated capture mode of configuration uses LogMiner and DataGuard's redo log transport mechanism. Once registered with the source database, the GoldenGate Extract process becomes implicitly RAC-aware and integrates with RMAN's archive log retention policy.

The LogMiner server running on the source database mines the redo stream and converts the change vectors to Logical Change Records (LCR). The LCRs are consumed by the Extract process that writes the replicated data to a local trail file. The data pump process reads the local trail and writes to the remote trail file, which is subsequently read by the Replicat. In integrated mode, the Replicat will apply the changed data as LCRs via a lightweight streaming API. In classic mode, the Replicat converts the LCRs to SQL (DML or DDL), which is applied to the target database.

The following diagram illustrates the changed data flow when GoldenGate is operating in the integrated capture mode:

A new feature of Oracle GoldenGate 12c is the integrated delivery mode. This long awaited performance enhancement is fully supported against Oracle database versions 11.2.0.4 and above. It provides better scalability and load balancing that leverages the database parallel apply servers for automatic dependency aware parallel Replicat processes. With integrated Replicat, there is no need for the GoldenGate administrator to manually split the delivery process into multiple threads and manage multiple parameter files.

The following diagram shows the processes involved in the integrated delivery configuration mode.

Both the integrated modes should be configured where possible to take advantage of the performance and management features.

Classic mode

Oracle GoldenGate 12c still supports the original Extract and Replicat configuration, known as the classic mode. Once the GoldenGate processes are configured in integrated mode, they can be manually switched by the GoldenGate administrator from integrated to classic and vice versa.

The following illustration describes the classic capture and delivery architecture:

Coordinated mode

The coordinated delivery option applies to the GoldenGate Replicat process when configured in the classic mode. It provides a performance gain by automatically splitting the delivered data from a remote trail file into multiple threads, which are then applied to the target database in parallel. GoldenGate manages the coordination across selected events that require ordering, including DDL, primary key updates, Event Marker System or Event Maker Interface (EMI), and SQLEXEC. Coordinated delivery can be used with both Oracle (from version 11.2.0.4) and non-Oracle databases.

DDL replication

Since Oracle GoldenGate 11g Release 2, support for DDL is mastered through the database log mining server in a similar fashion to DML in the integrated capture mode. DDL and DML replication are now independent of each other. In the earlier versions, DDL could only be replicated with DML and requires installation of additional GoldenGate modules. It is now possible to configure just DDL synchronization between Oracle databases.