To use OpenEdge Replication, you must activate after-imaging on the source database. Additionally, if you define a Replication Set, you must activate after-imaging on your target databases as well. When you enable after-imaging, the database engine writes notes containing a description of all database changes to the after-image logs. You can use this information generated by after-imaging to recover a database that was damaged when a failure caused the loss of either the database itself or its primary recovery (before-image) area.
Before you start using OpenEdge Replication, it is recommended that you calculate how much after-image volume, on average, your database currently generates. You can then use this average to estimate the network bandwidth that establishing replication for the database will require. After-image data plays the largest part in determining how much bandwidth you need.
Although you cannot calculate exact data volume, since it is dependent on the type of transactions within the application and how much activity is going on against the database, you can arrive at an estimate if you know the average amount of after-image volume on your system.
The details in the following sections provide information related to:
Calculating current database after-image volume
The role of the after-image extents in the Replication process
Using after-imaging with OpenEdge Replication
For more general information about database after-imaging, see OpenEdge Data Management: Database Administration.
Calculating current database after-image volume