Goal - Target objective

Enhanced Definition

In the context of z/OS Workload Manager (WLM), a "goal" represents a target objective or performance specification defined for a workload. It dictates the desired performance level (e.g., response time, throughput) that WLM should strive to achieve for a particular group of work, ensuring that critical applications receive the necessary system resources.

Key Characteristics

- Performance-Driven: Goals are quantitative performance targets, such as a response time (e.g., "90% of transactions complete in less than 0.5 seconds") or a throughput rate (e.g., "complete 50 batch jobs per hour").
- Service Class Assignment: Each goal is associated with a specific service class, which is a grouping of similar work (e.g., CICS transactions, critical batch jobs, DB2 threads) that share the same performance requirements.
- Importance Level: Goals are assigned an importance level (1-5, with 1 being most important) which WLM uses to prioritize resource allocation when contention occurs between different workloads.
- Dynamic Resource Management: WLM continuously monitors the actual performance of workloads against their defined goals and dynamically adjusts system resources (CPU, I/O, memory) to meet these objectives.
- Types of Goals: Common types include response time goals (for interactive or online work) and throughput goals (for batch or continuous processing).

Use Cases

- Online Transaction Processing (OLTP): Defining a response time goal for CICS transactions to ensure quick user interaction and business responsiveness.
- Critical Batch Processing: Setting a throughput goal for overnight batch jobs to ensure they complete within their allocated window, or a response time goal for individual steps within a critical batch stream.
- Database Access: Prioritizing DB2 or IMS database operations for high-priority applications by assigning them to a service class with a stringent response time goal.
- System Services: Ensuring core z/OS system tasks and utilities maintain optimal performance for overall system stability and responsiveness.
- Application Development and Testing: Allocating specific resources and performance targets for development and test environments to ensure consistent performance during testing cycles.

Related Concepts

Goals are the cornerstone of the z/OS Workload Manager (WLM), which is responsible for managing system resources. They are defined within a WLM policy and applied to service classes that categorize different types of work. WLM uses the defined goals, along with importance levels, to make intelligent decisions about dispatching priorities, CPU allocation, and other resource adjustments to meet the specified performance objectives. Goals effectively replaced the fixed dispatching priorities of older performance groups, providing a more dynamic and adaptive approach to workload management.

Best Practices:

Define Realistic Goals: Base goals on historical performance data, business requirements, and system capabilities to ensure they are achievable and meaningful.
Prioritize Critical Workloads: Assign higher importance levels and tighter goals to business-critical applications to guarantee their performance during peak loads.
Monitor and Tune Regularly: Use RMF (Resource Measurement Facility) and SMF (System Management Facilities) data to continuously monitor goal attainment and adjust WLM policies as needed.
Avoid Over-Specification: Do not create an excessive number of service classes or overly granular goals, as this can complicate management and potentially lead to inefficient resource allocation.
Test WLM Policy Changes: Always test new or modified WLM policies in a non-production environment before deploying them to the production system to prevent unintended performance impacts.