OpenEdge Management and OpenEdge Explorer: Configuration

Using the background writers and watchdog process
Using the background writers and watchdog process
On shared-memory systems, setting database background writer and watchdog processes can
improve database performance. Background writers continuously perform overhead functions
in the background.
Background writers
There are three types of background writers:
• 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.
The watchdog process
The watchdog process improves performance by cleaning up after improperly terminated
processes. It releases locks, backs out any live transactions, and releases shared-memory locks.
It also disconnects and cleans up the server's remote clients.
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