Mainframe, MVS and zOS Discussion

Hi,

What is work load manager(WLM) in mainframes? Is it something available in mainframes only? How does it help in defining performance of OS390/zOS?
Thnaks in advance

Workload Manager (WLM) is a z/OS tool to manage the system workload. I don't know if it can be used on any platform other than a z/Architecture machine (z/OS, z/VM, ...) although probably not. WLM is used to define workloads (for example, online, high-importance batch, low-importance batch, TSO, system tasks, high-importance started tasks, low-importance started tasks would be 7 possible workloads -- others could include DB2, MQ series, IMS; I've seen sites with 50 workloads defined). Once the workloads are defined, goals are set (for example, 95% of online transactions should complete in 2 seconds, or 90% of TSO transactions should complete in 5 seconds, or a started task should get 20% of the CPU when it is executing). WLM will monitor the workloads and adjust priorities of executing tasks to respond to the changing system environment. The site can allow WLM to control the initiators, in which case WLM will add or remove initiators (on a JES3 system) to meet the goals.

Broadly speaking, WLM does not define z/OS performance -- the site support group defines a policy which in turn defines the workloads and their relative importance as well as how they want WLM to measure the workload. WLM then implements that policy and manages the system resources to attempt to meet the policy goals. WLM is most useful when the CPU is running at 100% since that is when decisions about relative importance of jobs / tasks / TSO users / online transactions are most important, but WLM will usually improve performance of any z/OS system.

Thanks Robert.