As the database server writes rows to the logical log, it marks rows that should be replicated. Later, Enterprise Replication reads the logical log to obtain the row images for tables that participate in replication.
Informix database servers manage the logical log in a circular fashion; the most recent logical-log entries write over the oldest entries. Enterprise Replication must read the logical log quickly enough to prevent new logical-log entries from overwriting the logs Enterprise Replication has not yet processed. If the database server comes close to overwriting a logical log that Enterprise Replication has not yet processed, user transactions are blocked until Enterprise Replication can advance. (This situation is called DDRBLOCK mode and occurs only if the system is severely misconfigured.)
The row images that participate in replication are passed to Enterprise Replication for further evaluation.
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