Selecting a diagnostic tool

Degradation analysis (DEXAN for MVS) and impact analysis are diagnostic tools that offer complementary views of the same problem. Which one should you use? The answer depends on the kind of problem that you are experiencing and the kind of information that you are looking for.

Degradation analysis is effective as a general exception monitor, and as a diagnostic tool that deals with certain symptoms that indicate a tuning problem. Degradation analysis shows if a resource is unavailable or in contention. However, it provides no direct information about how to deal with problems resulting from workload contention. If a resource is in contention, you must gather additional information to identify the primary users of the resource.

Impact analysis is well suited for detailed analysis of workload contention problems that have been identified by DEXAN or exception analysis. Impact analysis can accurately identify the source of resource contention, because it focuses on workloads as they contend for resources.

You may find the following guidelines useful when you are deciding on the best diagnostic tool to use: If you want to gather detailed information on resource usage to help tune applications for best performance and to understand reserve capacity as indicated by idle states, use degradation analysis as your routine performance monitor. If your primary goal is to quickly solve acute performance problems, impact analysis offers you the best diagnostic capabilities.