When you set up your service definition, you identify the workloads, the resource groups, the service classes, the service class periods, and goals based on your performance objectives. Then you define classification rules and one or more service policies. This information makes up the base service definition.
A two-step process is required before the sysplex starts using a new service definition. First, you install the service definition onto the WLM couple data set. Second, you activate one of the service policies from the definition.
With a service policy, you can override specific goals or resource groups in your base service definition. In a typical scenario, you might define a base service definition that is appropriate for your normal business hours. Because you need to have at least one service policy defined, you might create an empty service policy called NORMAL. While the NORMAL service policy is in effect, there would be no overrides to the goals or resource groups in the base service definition. If you have a special business need to change your goals for offshift processing, you might then also create a service policy called OFFSHIFT. If you were to activate this policy at the end of the business day (either by invoking the VARY WLM,POLICY=policyname command or by using the “Activating a Service Policy” panel in the ISPF application), then the goal overrides in the OFFSHIFT service policy would be in effect until you switched back to NORMAL the next morning.
Defining service policies tells you more about how to define a policy, and also shows a few examples.
Note that you can override only goals, number and duration of periods, resource group assignments and values. All of the workloads, service class names, classification rules, scheduling environments, and application environments defined in the service definition remain the same for any policy. If you need to change any of these, you will need to change the base service definition, reinstall the service definition, and then activate a policy from that changed service definition.
Note, also, that you need to define all of your policies at the outset, while you are defining the rest of the service definition. Once the service definition is installed, then you can switch from one defined policy to another. If you need to create a new policy or change the overrides in an existing policy, you will need to reinstall the service definition with the new or changed policy definition before you can activate the new policy.
Figure 1 shows a service definition with two service policies.
