Tuning is the process of altering various
system values to improve overall performance
possible from any given configuration and work load. However, the
process does not include the acquisition and installation of additional
memory or devices, although in many cases such additions (when made
at the appropriate time) can vastly improve system operation and
performance.
On most systems, the work load is constantly changing. System
parameters that produce optimal performance at one time may not
produce optimal performance a short time later as the work load
changes. Your goal is to establish values that produce acceptable
performance under all of the changing work load conditions.
Before you undertake any action, you must recognize that the
following sources of performance problems cannot be cured by adjusting
system values:
Improper operation
Unreasonable performance expectations
Insufficient memory for the applications attempted
Inadequate hardware configuration for the work load,
such as too slow a processor, too few buses for the devices, too
few disks, and so forth
Improper device choices for the work load, such
as using disks with insufficient speed or capacity
Hardware malfunctions
Poor application design
Allowing one process to consume all available resources
When you make adjustments, you normally select a very small
number of values for change, based on a careful analysis of the
behavior you observed. You control system resources by tuning the
values of two types of parameters:
Parameter Type
Description
System parameters
The values set for system
parameters control system resources on a systemwide basis. The AUTOGEN
command procedure automatically sets system parameters to appropriate
values for your system configuration. AUTOGEN can also record feedback
from a running system to adjust those parameters based on the system's work
load.
OpenVMS Performance Management describes how to select the parameters
and new values that are likely to produce the desired changes.
The values set for limits and quotas
in each user authorization file (UAF) record control system resources
on a per-user basis. To control these values, use the Authorize
utility. For information, see the HP OpenVMS System Manager's Manual, Volume 1: Essentials.
Before
you undertake any tuning operation, be sure you are familiar with
the resource management mechanisms described in OpenVMS Performance Management. Understand
the nature of system values before adjusting them. Without the proper
level of understanding, you might degrade, rather than improve, overall
performance.
HP OpenVMS System Manager's Manual, Volume 2:... 
Performance Considerations
