The performance advisor in Tivoli® Performance Viewer provides advice to help tune systems for optimal
performance and provides recommendations on inefficient settings by
using the collected Performance Monitoring Infrastructure (PMI) data.
About this task
Obtain advice by clicking
Performance Advisor in Tivoli Performance Viewer. The performance advisor in Tivoli Performance Viewer provides more extensive advice than
the Performance and Diagnostic Advisor. For example, Tivoli Performance Viewer provides advice on setting the dynamic cache
size, setting the Java virtual machine (JVM) heap
size and using the DB2® Performance Configuration wizard.
- Enable data collection and set the PMI monitoring level
to Extended.
The monitoring levels that determine which
data counters are enabled can be set dynamically, without restarting
the server. These monitoring levels and the data selected determine
the type of advice you obtain. The performance advisor in Tivoli Performance Viewer uses the extended monitoring level;
however, the performance advisor in Tivoli Performance Viewer can
use a few of the more expensive counters (to provide additional advice)
and provide advice on which counters can be enabled.
For example,
the advice pertaining to session size needs the PMI statistic set
to All. Or, you can use the PMI Custom Monitoring Level to enable
the Servlet Session Manager SessionObjectSize counter. The monitoring
of the SessionSize PMI counter is expensive, and is not in the Extended
PMI statistic set. Complete this action in one of the following ways:
- PMI settings.
- Enabling Performance Monitoring Infrastructure using
the wsadmin tool.
- In the administrative console, click Monitoring and
Tuning > Performance Viewer > Current Activity.
- Simulate a production level load. Simulate a
realistic production load for your application, if you use the performance
advisor in a test environment, or do any other performance tuning.
The application must run this load without errors. This simulation
includes numbers of concurrent users typical of peak periods, and
drives system resources, for example, CPU and memory to the levels
that are expected in production. The performance advisor only provides
advice when CPU utilization exceeds a sufficiently high level. For
a list of IBM® business partners providing tools to drive
this type of load, see the performance: resource for learning information.
- Log performance data with Tivoli Performance Viewer.
- Clicking Refresh on top of the table of advice causes
the advisor to recalculate the advice based on the current data in
the buffer.
- Tuning advice displays when the Advisor icon is chosen
in the Tivoli Performance Viewer Performance Advisor. Double-click
an individual message for details. Because PMI data is
taken over an interval of time and averaged to provide advice, details
within the advice message display as averages.
Note: If the Refresh
Rate is adjusted, the Buffer Size must also be adjusted to enable
sufficient data to be collected for performing average calculations.
Currently 5 minutes of data is required. Hence, the following guidelines
intend to help you use the Tivoli Performance Advisor:
- You cannot have a Refresh Rate of more than 300 seconds.
- RefreshRate * BufferSize > 300 seconds. Buffer Size * Refresh
Rate is the amount of PMI data available in memory and it must be
greater than 300 seconds.
- For the Tivoli Performance Advisor to work properly
with Tivoli Performance Viewer logs, the logs must be at least 300
seconds of duration.
For more information about configuring user and logging settings
of Tivoli Performance Viewer, refer to the configuring Tivoli Performance
Viewer settings information.
- Update the product configuration for improved performance,
based on advice. Because Tivoli Performance Viewer refreshes
advice at a single instant in time, take the advice from the peak
load time. Although the performance advisors attempt to
distinguish between loaded and idle conditions, misleading advice
might be issued if the advisor is enabled while the system is ramping
up or down. This result is especially likely when running short tests.
Although the advice helps in most configurations, there might be situations
where the advice hinders performance. Because of these conditions,
advice is not guaranteed. Therefore, test the environment with the
updated configuration to ensure it functions and performs well.
Over a period of time the advisor might issue differing advice. The
differing advice is due to load fluctuations and run-time state. When
differing advice is received, you need to look at all advice and the
time period over which it was issued. You must take advice during
the time that most closely represents the peak production load.
Performance tuning is an iterative process. After applying advice,
simulate a production load, update the configuration that is based
on the advice, and retest for improved performance. This procedure
is continued until optimal performance is achieved.