Establishing the service definition

A service definition contains all of the information necessary to perform workload management processing. Workload management provides an online panel-driven application for establishing a service definition.

Much of the information you need to establish a service definition is contained in the performance objectives described in Establishing performance objectives. An important piece of information contained in the service definition is the classification rule.

A classification rule consists of a work qualifier and a service class. One set of classification rules exists for each service definition. However, you can have multiple service classes for each service definition. Using the workload management-supplied function, you establish the classification rule and define the service class by specifying one or more work qualifiers. The work qualifier associates incoming transactions with a particular service class, which represents a group of transactions with similar performance criteria (performance goals and business importance, for example). Work qualifiers can be the subsystem type, the IMS transaction name, the IMS transaction class, the inputting LTERM name, or the user ID. You can use any one of these values, or a combination of them, to assign the service class to a transaction. A service class has performance criteria defined for it. After a transaction is assigned a service class, the z/OS® Workload Manager processes it according to the performance criteria defined for that service class.

In the following example, the classification rule uses the transaction name as the work qualifier. It assigns all incoming transactions with the name of DEPOSIT to the service class IMSHIGH.

The performance goal for the IMSHIGH service class is a response time of less than 1 second. The business importance of 1 gives the DEPOSIT transactions priority, after they are scheduled by IMS, if contention for system resources occurs.

Recommendation: Specify multiple WLM service classes, differentiating by business importance and goals. Then classify your IMS transactions in the WLM policy by using the IMS transaction class as the work qualifier for the WLM service that best fits the response time goals of each transaction.

By assigning different WLM service classifications to different IMS transactions, you ensure that the WLM manages the z/OS resources in a manner that gives all IMS transactions the best possible chance of obtaining their response time goals

If you assign a single WLM service class to all of your IMS transactions, the WLM treats all IMS address spaces, including the control region, equally. This means that WLM assigns the same dispatch priority to all of these address spaces. If some of your transactions do not make their response time goals, WLM would not know which address space to give the higher priority to (it should be the IMS Control Region) and would not change the priority for any of them.