This file describes how to set the level of performance data to be collected for WebSphere resources. It also contains instructions for starting the Resource Analyzer. The following topics are included:
By default, performance data is automatically collected for WebSphere resources and for run-time resources. All data collection impacts performance in some way, and the impact on performance varies depending on the counter. Resource Analyzer represents the overhead cost associated with each counter as a rating of low, medium, or high. If a counter has a low-level rating, its performance cost is minor and usually involves a single addition or subtraction. A counter with a high-level rating has a higher cost and usually involves several calculations including multiplication, division, or both. For example, collecting the number of times a bean instance is passivated has a low impact on performance. Calculating the average response time on all methods of an enterprise bean's remote interface has a medium impact on performance; calculating the average number of methods being processed concurrently has a high impact. The associated rating (low, medium, or high) for each counter is listed in Performance data.
The resources in a WebSphere domain are instrumented so that statistical data can be collected. Instrumentation refers to the mechanism by which some aspect of the running system is measured (analogous to a meter attached to a resource). Each performance category has a default instrumentation level (independent of the cost rating for the counters in that category). The instrumentation level determines which counters are being collected for that category. If a category has a default instrumentation level of high, for example, all counters for that category with a high performance rating and lower are collected. If a category has a default instrumentation level of medium, all counters for that category with a medium rating and lower are collected. Some performance categories have a default instrumentation level of none, meaning that no data collection takes place unless you explicitly set a higher instrumentation level for that category.
The default instrumentation levels enable most of the available counters, but do not include counters whose performance impact is too high or counters that can become numerous. For example, enterprise bean method counters can become too numerous and costly to collect if a bean has many methods. The default instrumentation level for enterprise bean methods is low.
See Performance data for a listing of the default instrumentation levels for each performance category.
Instrumentation levels can be changed by using the WebSphere Advanced Administrative Console as follows:
In the Performance dialog box, the instrumentation level can be set per performance category and per resource instance. The current instrumentation level is represented by a small box icon with color stripes. The color key is as follows:
The color stripes indicate cumulative cost levels--an icon with blue and yellow stripes, for example, indicates that both low-impact and medium-impact counters are being collected. Similarly, an icon with blue, yellow, and red stripes indicates that all counters (high, medium, and low) for that resource are being collected.
Note that even though data is being collected for a particular resource, this data is not reported (not displayed by the Resource Analyzer) unless you explicitly enable data reporting for a resource from within the Resource Analyzer. See Monitoring data for instructions.
For running application servers. To specify the instrumentation level for a resource, or to change the level, perform the following steps in the console:
If a counter is not set for collection in the console (that is, the chosen instrumentation level excludes that counter), the counter does not appear as an entry in the tables or charts in the Resource Analyzer, even though other counters for that resource are displayed.
For stopped application servers. If you want to change the instrumentation levels for a server before it is started, use the EPM specification property for the application server. This property is on the Advanced tab of the property sheet. The value of this property takes either of the following formats. The first format sets the instrumentation level for all performance modules; the second sets the level for individual modules.
epm=level epm.module_name=level
where level is none, low, medium, or high, and module_name is one of the following: beanData, beanMethodData, orbThreadPool, connectionMgr, objectPools, transactionData, servletEngine. Multiple specifications can be separated by a colon as in the following example:
epm.beanData=medium:epm.transactionData=medium.
The EPM specification property is persistent across server starts. If no changes are made to the EPM specification property, the server uses the levels stored in the repository before the server was shut down (or the default levels if this is the first time the server is started). After a server is shut down, the value of the EPM specification property can have the format epm.module_name.xxx=level or epm.module_name.xxx.yyy=level
For example, the value can be epm.beanData.DefaultContainer.IncBean.low. It is recommended that you do not use this alternate format to change instrumentation levels because knowledge of the server configuration is required.
The Resource Analyzer is available as a separately downloaded file from the Web. Depending on your platform, use either the ra.bat file or the ra.sh file provided with the product. These scripts are available in the directory ra/bin where Resource Analyzer was installed--for example, on Windows NT systems, C:\ResourceAnalyzer\ra\bin\ra.bat. Before running the script, edit the script to change the variable WAS_ROOT to the location of the root directory where WebSphere is installed.
By default, Resource Analyzer looks for the administrative server on the host machine where the Analyzer is started. If the administrative server is running on another machine, specify its host and port number. For example, the following command invokes the Resource Analyzer on Windows NT systems:
C:\> ra.bat [host_name [port_number]]
Due to memory requirements, it is recommended that you run the Resource Analyzer on a separate machine from the administrative server.