What is a Replicat?

Replicat is a process that delivers data to a target database. It reads the trail file on the target database, reconstructs the DML or DDL operations, and applies them to the target database.

The Replicat process uses dynamic SQL to compile a SQL statement once and then executes it many times with different bind variables. You can configure the Replicat process so that it waits a specific amount of time before applying the replicated operations to the target database. For example, a delay may be desirable to prevent the propagation of errant SQL, to control data arrival across different time zones, or to allow time for other planned events to occur.

For the two common uses cases of Oracle GoldenGate, the function of the Replicat process is as follows:

Initial Loads: When you set up Oracle GoldenGate for initial loads, the Replicat process applies a static data copy to target objects or routes the data to a high-speed bulk-load utility.
Change Synchronization: When you set up Oracle GoldenGate to keep the target database synchronized with the source database, the Replicat process applies the source operations to the target objects using a native database interface or ODBC, depending on the database type.

You can configure multiple Replicat processes with one or more Extract processes and Data Pumps in parallel to increase throughput. To preserve data integrity, each set of processes handles a different set of objects. To differentiate among Replicat processes, you assign each one a group name

If you don't want to use multiple Replicat processes, you can configure a single Replicat process in parallel, coordinated, integrated mode.

Parallel mode Parallel Replicat supports all databases using the non-integrated option. Parallel Replicat only supports replicating data from trails with full metadata, which requires the classic trail format. It takes into account dependencies between transactions, similar to Integrated Replicat. The dependency computation, parallelism of the mapping and apply is performed outside the database so can be off-loaded to another server. The transaction integrity is maintained in this process. In addition, parallel replicat supports the parallel apply of large transactions by splitting a large transaction into chunks and applying them in parallel. See About Parallel Replicat.
Coordinated mode is supported on all databases that Oracle GoldenGate supports. In coordinated mode, the Replicat process is threaded. One coordinator thread spawns and coordinates one or more threads that execute replicated SQL operations in parallel. A coordinated Replicat process uses one parameter file and is monitored and managed as one unit. See About Coordinated Replicat Mode for more information.
Integrated mode is supported for Oracle Database releases 11.2.0.4 or later. In integrated mode, the Replicat process leverages the apply processing functionality that is available within the Oracle Database. Within a single Replicat configuration, multiple inbound server child processes known as apply servers apply transactions in parallel while preserving the original transaction atomicity. See About Integrated Replicat for more information about integrated mode.

You can delay Replicat so that it waits a specific amount of time before applying the replicated operations to the target database. A delay may be desirable, for example, to prevent the propagation of errant SQL, to control data arrival across different time zones, or to allow time for other planned events to occur. The length of the delay is controlled by the DEFERAPPLYINTERVAL parameter.