Unbuffered Logging

Databases on all server instances involved in replication must be created with logging.

Enterprise Replication evaluates the logical log for transactions that modify tables defined for replication. If a table defined for replication resides in a database that uses buffered logging, the transactions are not immediately written to the logical log, but are instead buffered and then written to the logical log in a block of logical records. When this occurs, HCL® OneDB® Enterprise Replication evaluates the buffer of logical-log records all at once. Buffered logging can require more time to flush the logs to disk. When you define a table for replication in a database created with unbuffered logging, Enterprise Replication can evaluate the transactions as they are produced.

Unlogged changes to a table, such as when data is added by a light append, can be replicated to other tables.

To create a database with unbuffered logging, use:

CREATE DATABASE db_name WITH LOG

To minimize impact on the system, HCL OneDB Enterprise Replication uses buffered logging whenever possible, even if the database is defined as unbuffered. For more information, see the section on CREATE DATABASE in the HCL OneDB Database Design and Implementation Guide.