LTL Generation

The number of bytes of information sent to Replication Server has a direct impact on the performance of the replication system; more data and commands received by Replication Server require more work and time to process.

In addition, more data also requires more network resources. There are several configuration options available for the Replication Agent that you can use to minimize this impact:

Using the RSSD. By reading replication definitions from the RSSD, the Replication Agent can send the column data in the same column order as specified by the replication definition. This allows Replication Server to bypass sorting the column information before processing. Furthermore, column names are not sent with the data, which reduces the number of bytes of information required.
Sending minimal columns. When an update operation occurs on a table, only a portion of the columns may have been altered. By sending the before and after images of only those columns that changed, the Replication Agent sends less information.

Note: Do not use minimal columns if the data in the replicate database involves custom function strings.
Batch mode. A Replication Agent must “wrap” transactions in a limited amount of administrative LTL for the Replication Server. In batch mode, the Replication Agent can wrap multiple commands in the same set of administrative commands, which reduces the overall LTL generated and processed by the network and the Replication Server.

In addition to batch mode, most Replication Agents have a “batch timeout” parameter, which allows a partial batch to be sent to the Replication Server after the Replication Agent waits a specified period of time and no additional transactions are received to fill the batch.

Note: Do not use Replication Agent batch mode if you use any Replication Server user-defined datatype (UDD) translations, either column-level or class-level.
Origin time. Each transaction sent to Replication Server has an origin queue ID. The origin queue ID may include the time that the transaction was committed at the primary database. If the origin time is not sent by the Replication Agent, the processing effort is reduced somewhat, but the quantity of LTL sent to the Replication Server is the same.

For a complete description of the Replication Agent configuration parameters that affect LTL output, see the Replication Agent Administration Guide.