Asynchronous Page Writer (APW) — The APW improves performance by performing overhead operations in the background. These operations provide available buffers, reduce the number of buffers that OpenEdge reads before writing to disk, and reduce the overhead associated with before-image checkpoints (the process of synchronizing the buffer pool of modified blocks to the database). You can start and stop an APW at any time without shutting down the database.
Before-image Writer (BIW) — The BIW improves performance by continually writing before-image buffers to disk. These writes occur in the background. BIWs are optional; however, they are highly recommended for improving I/O performance. You can run only one BIW per database. You can start and stop a BIW at any time without shutting down the database.
After-image Writer (AIW) — The 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. You can start and stop an AIW at any time without shutting down the database.
