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 below 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 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:
profile_root/logs/server_name
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.