Parallel replication processes leverage the apply processing functionality that is available within the Oracle Database in integrated mode. Within a single Replicat configuration, multiple inbound server child processes, known as apply servers, apply transactions in parallel while preserving the original transaction atomicity.

The following architecture diagram depicts the flow of change records through the various processes of a parallel replication from the trail files to the target database, for a non-integrated parallel Replicat.

The following is the description of the architecture diagram given above:

• The Mappers read the trail file and map records, forward the mapped records to the Master. The batches are sent to the Appliers where they are applied to the target database.
• The Master process consists of two separate threads, Collater and Scheduler. The Collater is responsible for managing and communicating with the Mappers, along with receiving the mapped transactions and reordering them into a single in-order stream. The Scheduler is responsible for managing and communicating with the Appliers, along with reading transactions from the Collater, batching them, and scheduling them to Appliers.
• The Scheduler controller communicates with the Scheduler to gather any necessary information (such as, the current low watermark position). The Scheduler controller is required for CDB mode for Oracle Database because it is responsible for aggregating information pertaining to the different target PDBs and reporting a unified picture. The Scheduler controller is created for simplicity and uniformity of implementation, even when not in CDB mode. Every process reads the parameter file and shares a single checkpoint file.