The "Blocking Session Count" Metric does not observe the Collection frequency and "number of occurrences" threshold in Enterprise Manager (Doc ID 1279015.1)

Last updated on NOVEMBER 27, 2015

Applies to:

Enterprise Manager for Oracle Database - Version 10.2.0.5 to 12.1.0.5.0 [Release 10.2 to 12.1]
Information in this document applies to any platform.
This applies to 10g, 11g and certain versions of 12c (only 12.1.0.3 cloud control and below)
Please note that from Cloud Control 12.1.0.4 onwards (which ships with the 12.1.0.6 plug-in), the contents of this article will not apply because UserBlock is calculated by the agent itself from 12.1.0.4 onwards (see for more information on this)

Symptoms

The collection schedule and number of occurrences is not observed for the "Blocking Session Count" metric in Enterprise Manager (10g, 11g and 12.1.0.3 Cloud control (and lower versions))  The Grid Control 11g online hint says:-

"To prevent false alerts due to spikes in metric values, the Number of Occurrences determines the period of time a collected metric value must remain above or below the threshold value before an alert is triggered or cleared. For example, if a metric value is collected every 5 minutes, and the Number of Occurrences is set to 6, the metric values (collected successively) must stay above the threshold value for 30 minutes before an alert is triggered. Likewise, once the alert is triggered, the same metric value must stay below its threshold for 6 consecutive occurrences (30 minutes) before it is cleared."

However when the collection schedule is set for 15 and the "number of occurrences" is set to 2 an alert is received immediately  (rather than waiting for 30 minutes)

Cause

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