How ADDM Computes Thresholds

Metric baselines are named snapshots of a target's past performance.

When baseline metrics are gathered, the AWR stores the high value and the low value for each metric. The technique that ADDM uses to compute a baseline threshold depends on the comparison operator that is used for spcifying the threshold , and on the associated high and low value.

If the metric comparison operator is a greater than (>), the warning threshold for the metric is computed as

Metric High Value * (1+Warning Percentage/100)

If the metric comparison is a less than (<), the warning threshold for the metric is computed as

Metric Low Value * (1-Warning %/100)

For example, if the high value for the metric Current Open Cursors Count is 500,

* the 85 percent warning threshold is 500*(1+85/100)= 925
* the 95 percent critical threshold is 500*(1+95/100)=975

raising an warning alert whenever the Current Open Cursos Count exceeds 925 or raising a critical alert whenever the Current Open Cursors Count exceeds 975.

if the low value for the metric Large Pool Free % is 300 MB,

* the 85 percent warning threshold is 300*(1-85/100) = 45 MB
* the 95 percent critical threshold is 300*(1-95/100) = 15 MB

raising a warning alert whenever the percentage of free space in the Large Pool fals below 45 MB or raising a critical alert whenever the free space in the Large Pool falls below 15 percent.