Workload Manager Overview

WLM, with the ability to run in goal mode, was first released with MVS/ESA version 5 in 1995. It is tightly integrated into the core of the operating system and available on all OS/390 implementations, including Sysplex configurations. IBM is strongly encouraging existing users to migrate to the the OS/390 environment so that they can take advantage of this product. The functionality of WLM is described only in very general terms within this book. IBM-specific terminology has been avoided wherever possible and replaced with terms that are familiar to the open systems literate reader. As a consequence, some detail has been sacrificed to aid readability and understanding. The notable exception is the terminology associated with goals, which is both descriptive and generic.

WLM Modes of Operation

WLM allows an OS/390 or Sysplex environment to run in two, mutually exclusive modes:

• Compatibility mode

• Goal mode

Dynamic switching between these modes is supported.

Compatibility Mode

This mode allows the Sysplex system resources to be managed in a traditional fashion, that is, manual tuning and defining rigid boundaries of resource limits and guarantees. It assumes that performance metrics are gathered and analyzed by skilled engineers who then tune the appropriate system parameters. These parameters can be changed and are usually set following an extended period of metrics gathering.

Goal Mode

The key feature within WLM is the ability to run in goal mode. In this mode, the system is driven by simple business goals, for example:

• Provide a given response time for a specific transaction type.

• Ensure that a certain percentage of transactions complete within the specified per transaction time.

• Ensure that a certain batch run is completed within a given time frame.

In goal mode, no manual configuration or performance tuning is required. Indeed it is not permitted. Tuning and resource management are carried out automatically, with system parameters changed on the fly. Something that cannot be carried out manually. All of this is performed by WLM and its components to ensure that the specified goals are met. Performance groups and performance domains, the traditional resource management tools of the system tuner, are not supported by WLM when running in goal mode. However, most of the components or tools used to manually control resource consumption are integrated and used in some form within WLM. WLM is tightly coupled with the underlying operating system and with system services, especially transaction based environments such as CICS and IMS. Thus it can measure consumption and control key, low level, resources such as processor, memory and disk storage I/O while integration with CICS and IMS allows performance to be measured at the level the business perceives, transaction response time.