# Percentiles

A percentile is the value of a variable below which a certain percent of observations fall. For example, the 95th percentile is the value (or score) below which 95 percent of the observations are found. Percentiles are calculated for rollups, dashboards, and report generation purposes.

capm320

HID_Percentiles

A percentile is the value of a variable below which a certain percent of observations fall. For example, the 95th percentile is the value (or score) below which 95 percent of the observations are found. Percentiles are calculated for rollups, dashboards, and report generation purposes.

Percentile monitoring is useful in measuring throughput data. This statistic more accurately reflects the required capacity of the monitored link for applications that are bandwidth sensitive. The 95th percentile says that 95 percent of the time, the bandwidth usage is below this amount. The remaining 5 percent of the time, the bandwidth usage is above that amount.

Metric values are aggregated during rollups.

By default,

`calculates the 95th percentile for some metrics. Metric families can include up to two more configurable percentile calculations.`CA Performance Management

Metric Property | Default | Values |

Percentile | Disabled or 95 | 0 or 95 |

Percentile2 | Disabled | 0-99 |

Percentile3 | Disabled | 0-99 |

A value of 0 disables the percentile calculation.

Changes to these properties generate Administration events. After you update the metric family, the percentile data is available for reporting within several poll cycles. For trend views, changes cause a gap in the trend line. For table views, changes affect the value of the percentile for time ranges when the change occurred. For example, in a daily time range, the value is inaccurate for one day.

When you disable a percentile, modify views that include the percentile to avoid an error in the view.

Calculate only percentiles that you need. Each percentile that you calculate might significantly affect system performance. For more information, see the capm Sizing Tool.

For more information, see Metric Family XML Structure. You can manually edit percentiles using the CA

`user interface. For more information, see Edit a Metric.`Performance Center

Three percentile values appear in the Metric Families table under the Monitoring Configuration menu for a Data Aggregator. A dash in the Percentiles column indicates that all three percentile values are equal to zero. For more information, see Manage Metric Families.

Percentile Calculations

Percentile calculations use the Microsoft Excel method.

Hourly and daily rollup uses the polled rate data. Weekly rollup performs the percentile calculation on the results of the daily rollups.

Percentiles are calculated in the database and exposed to the reports and dashboards.