Using the Monitoring Dashboard 15-9
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The number of values fetched is derived from the amount of time over which the stored samples can range, in which the sample interval is multiplied by the
maximum samples for the chart. The default sampling interval is 20 seconds and the default sample maximum is 100, which yields a time range of 2000 seconds, or
approximately 33.3 minutes.
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If the sampling interval used by the Harvester is different from the one configured for the Monitoring Dashboard, some distortion may be evident in the graphing of
that metric.
15.4.1.2 Custom Time Range Charts
Charts configured with a custom time range display collected metrics only. When you specify a custom time range for a chart and add a collected metric, the Monitoring
Dashboard fetches the metric’s values from the Archive that match the specified time range. These charts are static: once the Monitoring Dashboard displays collected
metrics in a custom time range chart, the values of those metrics are never updated.
Note the following:
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Custom time range charts never include real-time, polled metric values.
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As a convenience for creating custom time range charts, the Metric Browser includes a button labeled Collected Metrics Only. When you select this button,
the Metric Browser displays only collected metrics.
15.4.2 Sequence in which Metrics Data is Displayed
If the Harvester is configured to collected runtime MBean metrics, collection can begin independently of whether the Monitoring Dashboard is running. This section shows
the sequence of activity that occurs when the Monitoring Dashboard collects and displays metrics in current time range and custom time range charts.
1.
If the Harvester is configured to collect data for a metric, it starts to harvest that data after the server is started. The data is persisted in the Archive.
2.
When the Monitoring Dashboard is launched, the list of available built-in and custom views is displayed. However, the real-time polling of metric values
directly by JMX does not begin until one or more views are started.
3.
When a view containing a current time range chart is started:
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The Monitoring Dashboard begins polling the runtime MBean instances corresponding to the metrics contained in the chart.
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If the Harvester has collected data for this metric in the Archive, that data added to the chart immediately. The number of samples that the Monitoring
Dashboard obtains from the Archive corresponds to the time range for the chart.
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If the Harvester was not configured to harvest data for this metric, no historical data is retrieved from the Archive for the metric and therefore none
is displayed.
4.
When a view containing a custom time range chart is created, the Monitoring Dashboard fetches from the Archive the set of values for the metric that match the
custom time range specified for that chart. Once the values are displayed in the chart, the chart is never updated. The view in which a custom time range chart has
been added does not need to be started in order to have the values of its collected metrics displayed.
15-10 Configuring and Using the Diagnostics Framework for Oracle WebLogic Server
5.
As polled data values for a metric arrive in the Monitoring Dashboard, the new values are added to the chart. The oldest values obtained from the Archive, if
available, are purged.
The chart always displays the most current data. The maximum samples for a chart determines how many samples can be saved for metrics, in both current and
custom time range charts. After a chart reaches its maximum samples threshold, the oldest metric values are removed as newest arrive.
15.4.3 Notes about Metric Data Retention
