The advisors analyze the Performance Monitoring Infrastructure (PMI) data of WebSphere® Application Server using general performance principles, best
practices, and WebSphere Application Server-specific rules for
tuning.
About this task
This topic is only appropriate for AIX®, Linux®, and Windows operating
systems.The Performance and Diagnostic Advisor provides advice to help
tune systems for optimal performance and is configured using the WebSphere Application Server administrative console or the wsadmin tool
(scripting). The Performance and Diagnostic Advisor uses Performance
Monitoring Infrastructure (PMI) data to provide recommendations for performance tuning. Running in
the Java™
virtual machine (JVM) of the application server, this advisor periodically checks for inefficient
settings, and issues recommendations as standard product warning messages. View these
recommendations by clicking Troubleshooting > Runtime Messages > Runtime Warning in the
administrative console. Enabling the Performance and Diagnostic Advisor has
minimal system performance impact.
Procedure
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Ensure that PMI is enabled, which is default.
If PMI is disabled, see the enabling PMI using the administrative console information. To
obtain advice, you must first enable PMI through the administrative console and restart the server.
The Performance and Diagnostic Advisor enables the appropriate monitoring
counter levels for all enabled advice when PMI is enabled. If specific counters exist that are not
wanted, or when disabling the Performance and Diagnostic Advisor, you might
want to disable PMI or the counters that the Performance and Diagnostic Advisor enabled.
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If running WebSphere Application Server Network Deployment, you must enable PMI on both
the server and the administrative agent, and restart the server and the administrative agent.
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Click Servers > Application servers in the administrative console navigation
tree.
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Click server_name > Performance and Diagnostic Advisor Configuration.
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Under the Configuration tab, specify the number of processors on the server.
This setting is critical to ensure accurate advice for the specific configuration of the
system.
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Select the Calculation Interval.
PMI data is taken over time and averaged to provide advice. The calculation interval specifies
the length of time over which data is taken for this advice. Therefore, details within the advice
messages display as averages over this interval.
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Select the Maximum Warning Sequence.
The maximum warning sequence refers to the number of consecutive warnings that are issued
before the threshold is updated. For example, if the maximum warning sequence is set to 3,
then the advisor sends only three warnings, to indicate that the prepared statement cache is
overflowing. After three warnings, a new alert is issued only if the rate of discards exceeds the
new threshold setting.
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Specify Minimum CPU for Working System.
The minimum central processing unit (CPU) for a working system refers to the CPU level that
indicates a application server is under production load. Or, if you want to tune your application
server for peak production loads that range from 50-90% CPU utilization, set this value to
50. If the CPU is less than this value, some diagnostic and performance advice are still
issued. For example, regardless of the CPU level if you are discarding prepared statements at a high
rate, you are notified.
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Specify CPU Saturated.
The CPU saturated level indicates at what level the CPU is considered fully utilized. The
level determines when concurrency rules no longer increase thread pools or other resources, even if
they are fully utilized.
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Click Apply.
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Click Save.
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Click server_name > Performance and Diagnostic Advisor Configuration.
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Click the Runtime tab.
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Click Restart.
Select
Restart on the Runtime tab to reinitialize the
Performance and Diagnostic Advisor using the last configuration information
that is saved to disk.
This action also resets the state of the Performance and Diagnostic Advisor. For example, the current warning count is
reset to zero (0) for each message.
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Simulate a production level load.
If you use the Performance and Diagnostic Advisor in a test
environment, do any other tuning for performance, or simulate a realistic production load for your
application. 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 and Diagnostic Advisor provides advice when CPU utilization exceeds
a sufficiently high level only. For a list of IBM® business partners that provide tools to drive this type of
load, see the performance: resource for learning information.
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Select the check box to enable the Performance and Diagnostic Advisor.
Tip: To achieve the best results for performance tuning, enable the Performance and Diagnostic Advisor when a stable production-level load is
applied.
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Click OK.
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Select Runtime Warnings in the administrative console under the Runtime Messages in the
Status panel or look in the SystemOut.log file, which is located in the
following directory:
Some messages are not issued immediately.
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Update the product configuration for improved performance, based on advice.
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 that it functions and performs better than the previous configuration.
Over time, the
advisor might issue differing advice. The differing advice is due to load fluctuations and the
runtime state. When differing advice is received, you need to look at all advice and the time period
over which it is issued. Advice is taken 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.
What to do next
You can enable and disable advice in the Advice Configuration panel. Some advice applies
only to certain configurations, and can be enabled only for those configurations. For example,
unbounded Object Request Broker (ORB) service thread pool advice is only relevant when the ORB
service thread pool is unbounded, and can only be enabled when the ORB thread pool is unbounded. For
more information on Advice configuration, see the advice configuration settings information.
Note: This topic references one or more of the application server log files. As a
recommended alternative, you can configure the server to use the High Performance Extensible Logging
(HPEL) log and trace infrastructure instead of using
SystemOut.log ,
SystemErr.log,
trace.log, and
activity.log files on distributed and IBM
i systems. You can also use HPEL in conjunction with your native z/OS® logging facilities. If you are using HPEL, you can access all of your log and trace
information using the LogViewer command-line tool from your server profile bin directory. See the
information about using HPEL to troubleshoot applications for more
information on using HPEL.