The after-image file is used to enable recovery to the last transaction or to a point in time in the case of media loss. After-imaging is critical for a comprehensive recovery strategy.
The after-image file is like the before-image file in the sequential nature of its access. It does not have automatic reuse like the before-image file because it requires intervention from the administrator to reuse space. After-imaging is the only way to recover a database to the present time in the case of a media failure (disk crash). It also provides protection from logical corruption by its "point-in-time" recovery ability.
For example, assume a program accidentally runs and incorrectly updates every customer name to "Frank Smith." If you have mirroring, you now have two copies of bad data. With after-imaging, you can restore last night's backup and roll forward today's after-image files to a point in time just prior to running the program. After-image should be a part of every high-availability environment. For more details on implementing and managing after-image files, see OpenEdge Data Management: Database Administration.
