Using the performance advisor in Tivoli Performance Viewer

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.

1. Enable PMI in the application server.

   To monitor performance data through the PMI interfaces, you must first enable PMI through the administrative console before restarting the server.

   If running in a WebSphere® Application Server Network Deployment environment, you must enable PMI on both the server and on the administrative agent before restarting the server and the administrative agent.

2. 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:

   1. PMI settings.
   2. Enabling Performance Monitoring Infrastructure using the wsadmin tool.
3. In the administrative console, click Monitoring and Tuning > Performance Viewer > Current Activity.
4. 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.
5. Log performance data with Tivoli Performance Viewer.
6. Clicking Refresh on the table of advice causes the advisor to recalculate the advice based on the current data in the buffer.
7. 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:

   1. You cannot have a Refresh Rate of more than 300 seconds.
   2. 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.
   3. 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.

8. 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.