Release 10.1C: OpenEdge Replication:
User Guide
OpenEdge Replication agent
For the OpenEdge Replication server to succeed in keeping the source and target databases identical, it needs an OpenEdge Replication agent to receive information and perform updates to the target database. The OpenEdge Replication agent process receives configuration and operating instructions from the OpenEdge Replication server, including what actions to follow if connection to the OpenEdge Replication server is lost.
Figure 1–4 shows the OpenEdge Replication agent process in the OpenEdge Replication model.
Figure 1–4: OpenEdge Replication agent
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The OpenEdge Replication agent performs the actual process of updating the target database. The agent must reside on the target database machine and provides the following services:
- Updates the target database to keep it identical with the source database by using the AI blocks sent from the OpenEdge Replication server.
- Performs a continuous roll forward of the source database activity to the target database.
- Places the target database into Enhanced Read-Only mode. For more information about Enhanced Read-Only mode, see the "Enhanced Read-Only mode" section. For information about what your OpenEdge Replication installation supports, see the "Database access once OpenEdge Replication is running" section.
The OpenEdge Replication model with source and target databases, OpenEdge Replication server, and OpenEdge Replication agent coexists with a standard database model with its servers, brokers, and other processes.
Figure 1–5 illustrates the OpenEdge Replication model coexisting in a standard database environment.
Figure 1–5: OpenEdge Replication model
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As shown in Figure 1–5, the source and target databases can be on the same machine. However, the source and target database should reside on separate machines so the target can run if the source machine fails.
Designating a critical agent
OpenEdge Replication allows a maximum of two agents per server. You can designate one agent as critical when you want to automatically transition to that agent’s target database during failure processing. For example, if you have two target databases, only the database managed by a critical agent (with the
transition
property set toauto
) will automatically transition during failure processing.There can be, at most, one critical agent defined. If a second critical agent is configured, it will be changed to a noncritical agent. All agents by default are noncritical. To change an agent to critical, the
critical
property must be set to1
in thesource-db-name
.repl.properties
file. For more information, see the "OpenEdge Replication properties" section.
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