Oracle Database 11 g - Online Public Access Catalog

CHAPTER 4 ■ PERFORMANCE MANAGEMENT 221Adaptive Baseline Metric ThresholdsThe Oracle database uses performance alerts to warn you about any violations of thresholds forvarious activities in the database. However, specifying when the database should issue an alertis a complex task. The setting of alert thresholds is a difficult task because the expected metricvalues can vary based on the instance load and workload type.In the Oracle Database 11g release, the database uses the AWR baseline metric statistics todetermine alert thresholds. Once the database computes baseline statistics for a specifiedbaseline, you can align the metric thresholds with these AWR baselines. These thresholds aretermed AWR baseline metric thresholds. Using AWR baselines as the source for the metric statisticslets you specify adaptive thresholds for database performance. The new metric thresholds arecalled adaptive since they’re based on the system_moving_window baseline, which is, by definition,constantly changing.You can define AWR baseline alert thresholds either through the PL/SQL interface or throughDatabase Control. The following steps show you how to use Database Control to configureadaptive thresholds:1. Click the Server tab on the Database home page.2. Click the AWR Baselines link in the Statistics Management section.3. You’ll be on the AWR Baselines page. Click the Baseline Metric Thresholds link.4. Select the metric type you want, and click Edit Thresholds.5. On the Edit Thresholds page, specify critical and warning thresholds for the metric inthe Thresholds Settings section.6. Click Apply Thresholds to apply the threshold settings.You must specify three threshold settings for each metric for which you choose to configureadaptive thresholds:• Threshold Type: Choose from Significance Level, which indicates whether a metric is ator above a specified value (for example 1 in 100); Percentage of Maximum; and FixedValues.• Warning: Warning threshold.• Critical: Critical threshold.Enterprise Manager provides a starter set of thresholds based on online transactionprocessing (OLTP) or data warehouse workload profiles. Once you select the profile, the databaseautomatically configures adaptive thresholds for the appropriate group of metrics for theworkload you choose by using metrics data from the system_moving_window baseline.