DSPSTATS - Dispatcher Statistics

Enhanced Definition

`DSPSTATS` (Dispatcher Statistics) is a z/OS console command used to display real-time statistics about the z/OS dispatcher's activity. It provides crucial insights into CPU utilization, dispatch queue lengths, and the readiness of address spaces and enclaves to execute. This command is a fundamental tool for performance monitoring and problem determination in a mainframe environment. `DSPSTATS` is a z/OS operator command used to display real-time statistics related to the z/OS dispatcher. It provides a snapshot of how the system's CPUs are being utilized and how work (TCBs, SRBs, enclaves) is being dispatched across various address spaces. This command is crucial for performance monitoring and problem determination on a mainframe system.

Key Characteristics

- Console Command: Issued directly from the z/OS operator console or via an automated operations program using the D DSPSTATS command.
- Real-time Data: Provides a current snapshot of dispatcher activity, making it invaluable for immediate performance assessment.
- Granular Metrics: Displays detailed statistics including CPU readiness, dispatch queue depths, CPU utilization percentages (both system-wide and per address space/enclave), and wait times.
- System-wide or Specific Scope: Can show statistics for the entire system or be filtered to specific address spaces, job names, or enclaves for targeted analysis.
- Diagnostic Tool: Essential for identifying CPU bottlenecks, unresponsive applications, and understanding how the z/OS dispatcher is allocating resources.
- WLM Interaction: The statistics reflect the outcomes of the Workload Manager (WLM) policies, showing how WLM is influencing dispatching priorities and resource distribution.

Use Cases

- Performance Monitoring: Regularly check system-wide CPU utilization and identify periods of high demand or unusual activity.
- Bottleneck Identification: Pinpoint specific address spaces, jobs, or enclaves that are consuming excessive CPU or experiencing long dispatch waits, indicating potential performance issues.
- Workload Balancing Assessment: Evaluate how effectively the z/OS dispatcher is managing different workloads and if WLM goals are being met, potentially leading to WLM policy adjustments.
- Problem Determination: Diagnose unresponsive applications or system slowdowns by examining dispatch queue depths and CPU readiness to determine if tasks are waiting for CPU.
- Capacity Planning Input: While real-time, repeated captures of DSPSTATS output can contribute to understanding CPU usage trends for future capacity planning.

Related Concepts

DSPSTATS directly reports on the activity of the z/OS Dispatcher, which is the core component responsible for allocating CPU time to ready tasks and address spaces. Its output is heavily influenced by Workload Manager (WLM) policies, as WLM sets the dispatching priorities that the dispatcher adheres to. It provides a real-time view of CPU Utilization and Address Space activity, complementing historical data collected by RMF (Resource Measurement Facility) and SMF (System Management Facilities) for a comprehensive performance analysis.

Best Practices:

Regular Monitoring: Incorporate D DSPSTATS into routine system health checks, especially during peak processing hours or after significant workload changes.
Understand the Output: Familiarize yourself with the various fields and metrics (e.g., %READY, DISP Q LEN, CPU UTIL) to accurately interpret the data and identify anomalies.
Combine with Other Tools: Use DSPSTATS in conjunction with other monitoring tools like RMF, D OMVS,P (for UNIX System Services processes), or application-specific monitors for a holistic view of system and application performance.
Focus on Exceptions: Pay close attention to consistently high %READY values, long dispatch queue lengths, or specific address spaces showing unusual CPU consumption, as these often indicate performance bottlenecks.
Automate Logging: For trend analysis and historical review, consider automating the capture and logging of DSPSTATS output at regular intervals, especially in non-production environments.