The Oracle Database QoS Management metrics provide the information needed to systematically identify Performance Class bottlenecks in the system. The bottleneck for a particular Performance Class is the resource that contributes the largest total wait time to each work request in the Performance Class.
When Oracle Database QoS Management is working to improve the performance of a particular Performance Class, it attempts to add more of the bottleneck resource (such as CPU time) for that Performance Class, or to make the bottleneck resource available more quickly to work requests in the Performance Class. This makes the resource less available to other Performance Classes. The negative impact on the Performance Classes from which the resource is taken may be significantly smaller than the positive impact on the Service Performance Class that is getting better access, resulting in a net win for the system as a whole. Alternatively, the Performance Class being penalized may be less important than the one being helped.
The Oracle Database QoS Management metrics are used to find a bottleneck for a Service Performance Class as follows:
Oracle Database QoS Management computes the average number of layer visits per edge work request for each layer. The average number of layer visits per edge work request–which we can compute from the request counts for the Service Performance Class at each layer–tells us the relative importance of wait time at each layer. If each work request arriving at a database service causes five database calls, then the wait time in the database is five times as important as the wait time for the database service.
Oracle Database QoS Management computes the average wait per call for each resource at each server.
Analyzing the average wait per call and the total number of calls per Performance Class gives us the resource wait contribution within each PC's response time. The largest such contribution is the current bottleneck for the Service Performance Class.
For detailed information on Oracle Real Application Clusters administration, deployment, and performance, refer to the Oracle Real Application Clusters Administration and Deployment Guide.
About Oracle Database QOS Management
About Cluster Managed Database Services
Managing Cluster Managed Database Services
Viewing All Targets of a Cluster
Introduction to Managing Oracle Databases
Enterprise Manager Information Roadmap
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