Analyzing z/OS performance

This chapter discusses some aspects of z/OS performance, and the service-level reporting and analysis that you can perform using z/OS-generated data. The chapter shows you how to use IBM Z Performance and Capacity Analytics reports to analyze your system.

Once your organization has established service-level objectives, you need to see that those objectives are met consistently and to the best of the system’s capabilities.

These major resources can affect user response times:

• Processor
• Processor storage
• I/O
• Network

If you are not meeting service-level objectives, investigate the use of these resources to identify areas of contention.

Note: This book covers the processor, processor storage, and I/O resources. To investigate network resources, use the IBM Z Performance and Capacity Analytics Network Performance feature.

The discussion of each resource does not cover all the aspects of a computer system and environment that might influence that resource’s measurement and analysis. What specifically affects a transaction’s response time always depends on the circumstances at the time the event occurs or when the measurement sample is taken.

This chapter explains where the data comes from and how it is measured and recorded by the system. It then describes how to use the IBM Z Performance and Capacity Analytics reports to analyze system performance.

By analyzing reports and data for each resource, you can identify whether a performance or service problem truly exists. If so, you can identify more closely the source of the problem and what you can adjust to overcome it.

This chapter presents a top-down approach to monitoring the performance of your z/OS system and its major resources. When viewing performance data, you should take a total systems perspective. Each unit of work produced by a system requires more than just one resource. The first step is to look at daily reports to see if you are meeting service-level objectives. If not, you must look more closely at the major resources of the computer system.

The three main host resources needed to complete a unit of work such as a transaction or job are:

• Processors
• Processor storage
• I/O

Before installing new hardware or software products, evaluate all three major system resources to determine what the contention indicators are showing for available capacity. Ask the question "If I buy more, what will I receive in return?" One of the major factors when trying to determine the benefits of change is seeing the total picture first.