OpenEdge Getting Started: Installation and Configuration - Product ...

Using OpenEdge resources in Windows
Using OpenEdge resources in Windows
OpenEdge uses several operating system resources such as shared memory and
memory locks, processes, and client memory in Windows. You can plan OpenEdge
operations more effectively if you understand these resources.
Shared memory
Shared memory is an area in the system memory that multiple users can access
concurrently. OpenEdge stores shared resources in the shared-memory area, enabling
multiple users and servers access to each database. OpenEdge uses semaphores and
spin locks to synchronize the activities of server and self-service client processes that
are connected to a database. Each process uses its semaphore or relies upon the spin
lock when it must wait for a shared resource.
You can tune OpenEdge performance by reconfiguring the size of the following
shared-memory buffers:
• Database buffers — OpenEdge reads database blocks into the database buffer
pool. Larger buffers usually result in less disk I/O.
• Before-image (BI) buffers — OpenEdge stores BI notes in memory before
writing them to disk.
• After-image (AI) buffers — OpenEdge stores AI notes in memory before writing
them to disk.
OpenEdge also creates shared-memory tables to provide essential information on the
status of each process, server, transaction, and lock. These tables enable you to
control all of the database activities from one shared area.
Processes on Windows and UNIX platforms
OpenEdge provides the following optional processes to improve performance in
Windows and on UNIX platforms:
• Asynchronous Page Writer (APW) — Improves database 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
checkpointing (the process of synchronizing the buffer pool of modified blocks to
the database).
• Before-image Writer (BIW) — Improves performance by continually writing
before-image buffers to disk. These writes occur in the background.
• After-image Writer (AIW) — Improves performance by continually writing AI
buffers to disk soon after OpenEdge fills the buffers.
• OpenEdge Watchdog (PROWDOG) — Cleans up after improperly terminated
processes by releasing locks, backing out any live transactions and releasing
shared-memory locks, and disconnecting and cleaning up the server’s remote
clients.
OpenEdge Getting Started: Installation and Configuration 201