WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

instead of to an application server output log. This advisor also captures data
and gives advice about more components. Specifically, this advisor can capture
the following types of information:
► ORB service thread pools
► Web container thread pools
► Connection pool size
► Persisted session size and time
► Prepared statement cache size
► Session cache size
► Dynamic cache size
► JVM heap size
► DB2 performance configuration
The Performance Advisor in Tivoli Performance Viewer provides more extensive
advice than the Performance and Diagnostic Advisor. Running the Performance
Advisor in Tivoli Performance Viewer can require plenty of resources and impact
performance. Use it with care in production environments.
7.9.4 WebSphere request metrics
PMI provides information about average system resource usage statistics but
does not provide any correlation between the data. Request metrics, in contrast,
provide data about each individual transaction and correlate this data.
Overview
Request metrics gather information about single transactions within an
application. The metric tracks each step of a transaction and determines the
process time for each of the major application components. Several components
support this transaction metric:
► Web server plug-ins
► Web container
► EJB container
► JDBC calls
► Web services engine
► Default messaging provider
The amount of time that a request spends in each component is measured and
aggregated to define the complete execution time for that transaction. Both the
individual component times and the overall transaction time can be useful
metrics when trying to gauge user experience on a site. The data allows for a
hierarchical by response time view for each individual transaction. When
debugging resource constraints, these metrics provide critical data at each
component. The request metric provides filtering mechanisms to monitor
Chapter 7. Performance, scalability, and high availability 273