Oracle Adaptive Thresholds

Oracle Tips by Burleson Consulting

This is an excerpt from "Oracle 10g New Features for Administrators" by Ahmed Baraka.

New in Oracle Database 10g Release 2, adaptive thresholds use statistical measures of central tendency and variability to characterize normal system behavior and trigger alerts when observed behavior deviates significantly from the norm.

As a DBA, you designate a period of system time as a metric baseline which should represent the period of normal activity of your system. This baseline is then divided into time groups. You can specify critical and warning thresholds relative to the computed norm.

Metric Baselines and Thresholds Concepts

Metric baselines are of two types:

o Static baselines are made up of a single user defined interval of time.

o Moving window baselines are based on a simple functional relationship relative to a reference time.

They are currently defined as a specific number of days from the past.

Two types of adaptive thresholds are supported:

o Significance level thresholds: The system can dynamically set alert thresholds to values representing statistical significance as measured by the active baseline. Alerts generated by observed metric values exceeding these thresholds are assumed to be unusual events and, therefore, possibly indicative of, or associated with, problems.

o Percent of maximum thresholds: You can use this type of threshold to set metric thresholds relative to the trimmed maximum value measured over the baseline period and time group. This is most useful when a static baseline has captured some period of specific workload processing and you want to signal when values close to or exceeding peaks observed over the baseline period.

Metric Baselines and Time Groups

The supported time grouping schemes have the daily and weekly options.

The daily options are:

o By hour of day: Aggregate each hour separately for strong variations    across hours.

o By day and night: Aggregate the hours of 7:00 a.m. to 7:00 p.m. as day    and 7:00 p.m. to 7:00 a.m. as night.

o By all hours: Aggregate all hours together when there is no strong daily    cycle.

The weekly time grouping options are:

o By day of week: Aggregate days separately for strong variations across    days.

o By weekday and weekend: Aggregate Monday to Friday together and    Saturday and Sunday together.

o By all days: Aggregate all days together when there is no strong weekly    cycle.

Enabling Metric Baselining

Before you can successfully use metric baselines and adaptive thresholds, you must enable that option by using Enterprise Manager. Internally, Enterprise Manager causes the system metrics to be flushed, and submits a job once a day that is used to compute moving-window baseline statistics. It also submits one job once every hour to set thresholds after a baseline is activated.

You can enable metric baselining from the Database Home page | Related Links | Metric Baselines | Enable Metric Baselines