Goal Mode - WLM service policy

Enhanced Definition

Goal Mode is the primary operational mode of the z/OS Workload Manager (WLM) where performance objectives are defined for workloads, and WLM dynamically manages system resources to achieve these goals. It allows an installation to specify desired performance for different types of work rather than just static priorities, ensuring critical applications meet their service level agreements.

Key Characteristics

- Performance Objectives: Allows defining specific performance goals such as response time (e.g., 1 second for CICS transactions), velocity (e.g., 50% CPU dispatchability for batch jobs), or execution time.
- Dynamic Resource Management: WLM continuously monitors system performance and dynamically adjusts resource allocation (CPU, I/O, memory) across different workloads to meet their defined goals.
- Service Classes: Workloads are categorized into service classes, each with a defined performance goal, importance, and optional resource group limits.
- Policy Activation: A WLM service policy is activated via the V WLM,POLICY=policyname operator command or during IPL, applying the defined goals and rules to the entire z/OS sysplex.
- Sysplex-wide Management: In a Parallel Sysplex environment, WLM coordinates resource management across multiple z/OS images to achieve consistent performance goals for distributed workloads.
- Importance Levels: Goals are assigned an importance level (1-5, 1 being most important) which WLM uses to prioritize resource allocation when contention occurs.

Use Cases

- Prioritizing Online Transactions: Ensuring critical CICS or IMS transactions (e.g., customer service, financial transactions) consistently achieve sub-second response times, even under peak load.
- Managing Batch Workloads: Defining velocity goals for high-priority batch jobs (e.g., end-of-day processing, payroll) to ensure they complete within their allotted processing windows.
- Resource Isolation: Using resource groups within a service policy to cap CPU or memory usage for specific workloads (e.g., development or test environments) to prevent them from impacting production.
- Database Performance: Setting performance goals for DB2 or IMS database access, ensuring queries and updates from critical applications receive adequate resources.
- Mixed Workload Environments: Effectively managing diverse workloads (online, batch, started tasks, TSO) on a single z/OS system, balancing their performance needs according to business priorities.

Related Concepts

Goal Mode is the core operational paradigm of the Workload Manager (WLM), which is a fundamental component of z/OS. It relies heavily on the definitions within a WLM service policy, which includes service classes, report classes, and resource groups. These policies are stored in the WLM couple dataset in a sysplex or on a single system, often configured via the WLM ISPF application. WLM interacts directly with the MVS dispatcher and other system components to manage CPU, I/O, and memory, ensuring that applications like CICS, IMS, DB2, and JES jobs meet their performance objectives.

Best Practices:

Define Measurable Goals: Set clear, quantifiable performance goals (e.g., 90% of transactions complete in < 0.5 seconds) rather than vague objectives.
Monitor and Tune Regularly: Continuously monitor WLM performance using tools like