Network Deployment (Distributed operating systems), v8.0 > Reference > Administrator best practices

PMI data classification

This topic describes the Performance Monitoring Infrastructure (PMI) data classification.

The static component consists of a name, ID and other descriptive attributes to identify the data. The dynamic component contains information that changes over time, such as the current value of a counter and the time stamp associated with that value.

The PMI data can be one of the following statistic types (these statistic types follow the J2EE 1.4 Performance Data Framework):

PMI data statistic types. PMI must be enabled before the server starts. If PMI is enabled after the server is started, the server needs to be restarted to start the PMI.

Statistic type Description Example
CountStatistic Represents a running count of a given value. Number of Servlet requests
AverageStatistic Represents a simple average. Keeps track of total, count, min, and max. The average can be derived by total and count. (This type is WebSphere extension to J2EE Performance Data Framework) Average HttpSession size in bytes.
TimeStatistic Same as AverageStatistic, except that the unit of measure is milliseconds or seconds. Average Servlet response time.
RangeStatistic Represents a time-weighted average. Keeps track of current, low water mark, high water mark, time-weight total, and integral. Number of concurrent Servlet requests.
BoundedRangeStatistic Same as RangeStatistic, with lower bound and upper bound. JDBC connection pool size.

The following diagram shows the statistic class hierarchy:



A unique ID that identifies the Statistic within the given Stats (WebSphere PMI extension)


Statistic name


Unit of measurement for the statistic


Textual description of the statistic


Time the first measurement was taken


Time the most recent measurement was taken



Count since the measurement started



Value since the measurement started


(WebSphere PMI extension. This is the same as the TimeStatistic defined in J2EE 1.4, except that it is used to track non-time-related measurements like byte size, etc.)


Number of measurements


Sum of the values of all the measurements


Minimum value


Maximum value



Upper limit of this attribute


Lower limit of this attribute



Current value of this attribute


Lowest value of this attribute


Highest value of this attribute


Time-weighted sum of this attribute [time-weighted average = integral / (lastSampleTime - startTime] (WebSphere PMI extension)

In WAS, Version 4, PMI data was classified with the following types:

These PMI data types continue to be supported through the PMI client API. Statistical data types are supported through both the PMI API and Java Management Extension (JMX) API.

In WAS, v4 and v5, CountStatistic data require a low monitoring level, and TimeStatistic data require a medium monitoring level. RangeStatistic and BoundedRangeStatistic require a high monitoring level. There are a few counters that are exceptions to this rule. The average method response time, the total method calls, and active methods counters require a high monitoring level. The Java virtual machine counters, SerializableSessObjSize, and data tracked for each individual method (method level data) require a maximum monitoring level. Also, the level maximum enables synchronized update to all the statistic types.

WAS Versions 6.0 and above deprecate the monitoring levels (Low, Medium, High, and Max) and introduces fine-grained control to enable/disable statistics individually. The fine-grained control is available under the custom option. Refer to Enable PMI for more details.

In order to reduce the monitoring overhead, updates to CountStatistic, DoubleStatistic, AverageStatistic, and TimeStatistic are not synchronized. Since this data tracks the total and average, the extra accuracy is generally not worth the performance cost. RangeStatistic and BoundedRangeStatistic are very sensitive; therefore, they are always synchronized.

To enable synchronized updates for all the statistic types enable the 'Use sequential update' option. Refer to Enable PMI for details.
Performance Monitoring Infrastructure (PMI)
Monitor overall system health


Search Tips   |   Advanced Search