Introduction to Replication Agents

A Replication Agent is a Replication Server client that retrieves information from the transaction log for a primary database and formats it for the primary Replication Server. RepAgent is the Replication Agent component for Adaptive Server.

Replication Agent detects changes to primary data and ignores changes to nonprimary data. Using Log Transfer Language (LTL), a subset of Replication Control Language (RCL), Replication Agent sends changes in primary data to the primary Replication Server, which distributes the information to replicate databases.

The Replication Agent connections status is derived from the status of the Replication Agent thread in the Replication Server, and the status of the Replication Agent process that is extracting data from the primary database. If either the Replication Agent thread or the Replication Agent process has stopped running, the RMS returns a suspended state. The RMS also returns a description if either of the components is not running.

Sybase provides Replication Agent components for other non-ASE data servers, including IBM DB2 Universal Database, Microsoft SQL Server, and Oracle. See the Replication Server Heterogeneous Replication Guide and the Replication Server Options documentation for the databases actively supported by Replication Server.

Replication Agent for DB2 is the Replication Agent component for the z/OS-based DB2 Universal Database. Sybase Replication Agent is the Replication Agent component for DB2 Universal Database (on UNIX and Windows platforms), Microsoft SQL Server, and Oracle.

RepAgent is an Adaptive Server thread. Replication Agent for DB2 is a separate process that resides on the z/OS host. Sybase Replication Agent is a separate application that resides on a UNIX or Windows host.

A Replication Agent performs:

Logs in to the Replication Server.
Sends a connect source command to identify the session as a log transfer source and to specify the database for which transaction information will be transferred.
Gets the name of the maintenance user for the database from the Replication Server. RepAgent filters out operations executed by the maintenance user, unless the send_maint_xacts_to_replicate or send_warm_standby_xacts configuration parameter is set to true.
Requests the secondary truncation point for the database from the Replication Server. This returns a value, called the origin queue ID, that RepAgent uses to find the location in the transaction log where it is to begin transferring transaction operations. The Replication Server has already received operations up to this location.
Retrieves records from the transaction log, beginning at the record following the secondary truncation point, and formats the information into LTL commands.

Replication Agent Overview
A Replication Agent is a Replication Server client that retrieves information from the transaction log for a primary database and formats it for the primary Replication Server. RepAgent is the Replication Agent component for Adaptive Server.
Format of the Origin Queue ID
The origin queue ID is a unique 32-byte binary string that increases in value as each new log record is transferred. The value must increase, because Replication Server ignores records with an ID lower than the highest ID stored in the inbound queue.
Replication Agent Products
Replication Agent products extend the capabilities of Replication Server by allowing non-Sybase database servers to serve as primary database servers in a Sybase replication system.
Replication Server and LTL Compatibility
Replication Agents and Replication Server negotiate the version of LTL to use for the session. This ensures that Replication Agents written for earlier versions of Replication Server remain compatible with more recent and current versions.