Oracle Database Quality of Service (QoS) Management bases its decisions on observations of how long work requests spend waiting for resources.

Examples of resources that work requests can wait for include hardware resources, such as CPU cycles, disk I/O queues, and Global Cache blocks. Other waits can occur within the database, such as latches, locks, pins, and so on. Although the resource waits within the database are accounted for in the Oracle Database QoS Management metrics, they are not managed or specified by type.

The response time of a work request consists of execution time and various wait times; changing or improving the execution time generally requires application source code changes. Oracle Database QoS Management therefore observes and manages only wait times.

Oracle Database QoS Management uses a standardized set of metrics, which are collected by all the servers in the system. There are two types of metrics used to measure the response time of work requests: performance metrics and resource metrics. These metrics enable direct observation of the wait time incurred by work requests in each Performance Class, for each resource requested. Since the work request traverses the servers, networks, and storage devices that form the system. Another type of metric, the Performance Satisfaction Metric, measures how well the Performance Objectives for a Performance Class are being met.