What does the Overall Capacity (%) metric include?
Overall Capacity is the highest of the four numbers in Enterprise Manager.
This number is generated by a heuristic that looks at other metrics to see where the weak point is in the system. For example, if the CPU is running well but the EM has filled up 95% of memory, then the overall capacity will be 95%. This metric will likely be the "one" health metric to pay attention to as an EM administrator.
The following metrics are examined when computing the overall capacity:
Health: Harvest Capacity (%) - how is the EM doing when it processes data every 15 seconds.
Health: Heap Capacity (%) - how much memory is being used. Takes a running average of the last 4 minutes.
Health: Incoming Data Capacity (%) - how well is the EM processing the incoming flow of data from Agents.
Health: Smartstor Capacity (%) - how well is the EM writing metric data to disk.
The Enterprise Manager Overall Capacity (%) metric estimates the percentage of the Enterprise Manager capacity that is being consumed.
The Overall Capacity (%) metric is computed in part from the following contributing metrics, which are shown in the metric browser tree under Enterprise Manager | Health:
- CPU Capacity (%)
- GC Capacity (%)
- Harvest Capacity (%)
- Heap Capacity (%) metric (see page 136)
- Incoming Data Capacity (%)
- SmartStor Capacity (%)
The Overall Capacity (%) metric is more valuable over a long period rather than for a specific 15-second time slice. Because the Overall Capacity metric is based on real-time metrics, the Overall Capacity value can spike quite a bit higher than 100 percent. The spike can occur, for example, because the hardware I/O subsystem overloads briefly. However, the Enterprise Manager tends to recover from these spike situations automatically when they are not long-lasting. In general, a spike (for example, to 200 percent) is not cause for concern if it is transient.
However, over a long period the ideal average Overall Capacity is 75 percent or less.
During time periods that the Overall Capacity (%) metric spikes to high values, at least one of the other contributing metrics probably also shows a spike. Investigating and understanding the source of the secondary spike can help pinpoint the root cause of the resource issue. For example, you might find the problem by looking at Heap Capacity (%) metric which feeds into Overall Capacity (%) metric.
Viewing the Overall Capacity metric in Historical mode is useful for a general, comparative view of Enterprise Manager capacity status. However, the Enterprise Manager workload is complex, and various aspects of the workload affect the Overall Capacity metric in different, nonlinear ways.
For instance, the duration of SmartStor maintenance tasks (spool to data conversion and reperiodization) can be an important indicator of Enterprise Manager capacity. However, these maintenance tasks do not directly participate in the Overall Capacity calculation. The SmartStor maintenance tasks cause an increase in CPU and heap utilization. The increased utilization results in an increase in capacity percentage, but the magnitude of the increase does not reflect the full impact of SmartStor maintenance issues.
The Overall Capacity metric is focused primarily on how an Enterprise Manager handles the agent metrics workload. This metric does not directly evaluate capacity with respect to the application triage map or CA CEM data. For example, the Overall Capacity metric does not reflect overloaded Enterprise Manager services or APM database I/O issues.