Release 10.1B: OpenEdge Replication
User Guide
Source and target databases
OpenEdge Replication makes a copy of one database onto another and keeps those two databases identical, as seen in Figure 1–1.
Figure 1–1: OpenEdge Replication from one site to another
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As shown in Figure 1–1, one database must be considered the source and the other the target.
The source database
The source database is the database that can be updated by users. The source database:
- Is where users do their work and make their database updates.
- Has both write access and read access.
- Is not considered a source database until it is enabled as an OpenEdge Replication source database.
- Is the database from which the OpenEdge Replication server replicates data to the target database.
- Must have after-imaging activated. The after-imaging feature lets you recover a database that was damaged when a failure caused the loss of the database or primary recovery (before-image) area.
When you enable after-imaging, the database engine writes notes containing a description of all database changes to the after-image files.
- Uses after-imaging (AI) to capture all database activity performed. This activity is then sent to the target database.
The target database
The target database is an identical copy of the source database. A second target database can be set up for additional redundancy. The target database:
- Originates from the source database and contains the same data, schema, and logical structure as the source database.
- Is updated solely by the OpenEdge Replication agent.
- Does not allow database updates by anything other than OpenEdge Replication.
- Permits queries and reports by users, as well as any non-database write activity (database utilities, for example) if OpenEdge Replication Plus is installed. For information on what your OpenEdge Replication installation supports, see the "Database access once OpenEdge Replication is running" section. See the "Utilities and OpenEdge Replication" section for supported non-database write activity.
Figure 1–2 shows the source and target databases in the OpenEdge Replication model.
Figure 1–2: Source and target databases Note: The source and target databases should reside on separate machines so the target can run if the source machine fails.
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