The OpenEdge Replication model—with source and target databases, OpenEdge Replication server, and OpenEdge Replication agent—coexists with a standard database model and its servers, brokers, and other processes.
The following figure illustrates the OpenEdge Replication model coexisting in a standard database environment with TCPIP communication.
Figure 6. OpenEdge Replication model
Although the source and target databases can reside on the same machine, it is beneficial to locate them on separate machines so the target can run if the source machine fails.
The Asynchronous Page Writer (APW) keeps writable buffers at a low count. The APW ensures that a supply of empty buffers is available so the database engine does not have to wait for database buffers to be written to disk.
The After-image Writer (AIW) improves performance by continually writing after-image (AI) buffers to disk soon after OpenEdge fills the buffers. The after-imaging feature lets you recover a database that was damaged when a failure caused the loss of the database or primary recovery (BI) area. When you enable after-imaging, OpenEdge writes notes to the after-image files that contain a description of all changes to the database. You can run only one AIW process per database.
