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
- 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.
- 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.
- Click Servers > Application servers in the
administrative console navigation tree.
- Click server_name > Performance and Diagnostic Advisor Configuration.
- 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.
- 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.
- 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.
- 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.
- 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.
- Click Apply.
- Click Save.
- Click server_name > Performance and Diagnostic Advisor Configuration.
- Click the Runtime tab.
- 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.
- 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.
- 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.
- Click OK.
- 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.
- 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.