Content deleted Content added
Line 12:
Finally the system administrator assigns an importance to each service class to tell WLM which service classes should get preferred access to system resources if the system load is too high to allow all work to execute. The service classes and goal definitions are organized in service policies together with other constructs for reporting and further controlling and saved as a service definition for access to WLM. The active service definition is saved on a couple data set which allows all [[z/OS]] systems of a [[Parallel Sysplex]] cluster to access and execute towards the same performance goals.
WLM is a closed control mechanism which
[[Image:PI02.jpg|thumb|400px|Definition of Performance Index|left]] The performance index for a service class is a single number which tells whether the goal definition could be met, has been overachieved or was missed. WLM modifies the access of the service classes based on the achieved performance index and importance. For this it uses the collected data to project the possibility and result of a change. The change is executed if the forecast comes to the result that it is beneficial for the work based on the defined customer expectations. It should be noted that WLM uses a data base ranging from 20 seconds to 20 minutes to contain a statistically relevant basis of samples for its calculations. Also in one decision interval a change is performed for the benefit of one service class to maintain a controlled and predictable system.
| |||