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IBM? InfoSphere? Data Replication-CDC Replication is a replication solution that captures ongoing database changes and passes them to the target database, message queue, or ETL solution (such as InfoSphere DataStage?) based on the table mapping configured in the InfoSphere Data Replication Management Console GUI application.

For critical information management activities such as dynamic data warehousing, master data management, application consolidation or migration, operating BI, and enabling SOA projects, CDC Replication can capture data changes and deliver them at high speed in a less impact way. In addition, CDC Replication can help reduce processing overhead and network traffic by sending only the changed data. Replication can be performed continuously or periodically. After the data is transferred from the source server, it can be remapped or transformed in the target environment.

The following figure shows the key components of CDC Replication.

The following list describes the key components of the InfoSphere Data Replication architecture: Access Server-controls all non-command-line access to the replication environment. When you log in to Management Console, you connect to Access Server. You can turn off Access Server on the client workstation without affecting the ongoing data replication activity between the source server and the target server. Manage API-runs as an optional programming interface based on Java. You can use this API to script operation configurations or interactions. Application Agent-acts as an agent on the target to handle changes sent by the source. Command line interface-allows you to manage data stores and user accounts independently of Management Console, as well as perform administrative scripting. Communication layer (TCP/IP)-acts as a private network connection between the source and destination. Source and destination data stores-represents the data files and CDC Replication instances required for data replication. Each data store represents the database you want to connect to and acts as a container for the table. Tables that are made available for replication are included in the data store. Management Console-allows you to configure, monitor, and manage replication on various servers, specify replication parameters, and initiate refresh and mirror operations from client workstations. In addition, Management Console allows you to monitor replication operations, wait times, event messages, and other statistics supported by the source or destination data store. The monitors in Management Console are designed for time-critical work environments that require continuous analysis of data movements. After setting up replication, you can turn off Management Console on the client workstation without affecting the ongoing data replication activity between the source server and the target server. Metadata-information that represents tables, maps, subscriptions, notifications, events, and other details of the data replication instance you set up. Mirror-copy changes to the target table or accumulate source table changes and copy them to the target table later. If two-way replication is implemented in the environment, you can mirror back and forth between the source and destination tables. Refresh-initially synchronizes the table from the source database to the destination. This will be read by the refresh reader. Replication engine-used to send and receive data. The process used to send replicated data is the source capture engine, and the process used to receive replicated data is the target engine. The CDC Replication instance can run as both the source capture engine and the target engine. Single fetch-acts as a log reader and log parser component for source only. It examines and analyzes the source database logs for all subscriptions on the selected data store.

Not all CDC Replication engines use "single extract". For CDC Replication Engine for DB2? For I, which has an extractor job (acting as a log reader) and a "mirror" job (to perform mirroring functions).

Source transformation engine-handles row filtering, key columns, column filtering, transcoding, and other data to be propagated to the target data storage engine. Source database logs-maintained by the source database for its own recovery. The CDC Replication log reader examines these logs during mirroring and filters out tables that are not in the scope of replication. Target transformation engine-processes data and value conversion, transcoding, user exit, collision detection, and other data on the target data storage engine. There are two replication destinations (not databases) that are used only for destinations: JMS messages-act as JMS message destinations (queues or topics) for row-level operations created as XML documents. InfoSphere DataStage-handles changes passed from CDC Replication that can be used by InfoSphere DataStage jobs.

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