The MVS Component of CPExpert

(Applies only to Compatibility Mode)


The relationship between large IBM computers, the processor storage they use, and the auxiliary storage backing the processor storage has become extremely complex. The complexity increases with each new technological advancement.

IBM has responded to this complexity by providing increasingly sophisticated system control programs to manage the configuration.

Each new version of MVS provides enhanced system management capabilities. Each new version generally provides more control opportunities for installations to tailor MVS's management of system resources to their own configuration and management objectives.

Each new version is supplied with default values for the various options, and IBM clearly states that many of the defaults should be changed in response to individual workloads and individual performance objectives.

Unfortunately, many installations do not consistently take advantage of the MVS system management capabilities. These installations do not always achieve optimal performance because of a lack of staff to conduct performance analysis studies or because their knowledgeable people are too busy with other issues.

The MVS Component of CPExpert analyzes overall system performance, processing data contained in your MXG, SAS/Service Vision, or CA-MICS performance data base. The MVS Component currently analyzes system performance in the following major areas affected by MVS controls:

 
System paging controls and paging subsystem (whether the paging rate is high, whether sufficient local page data sets are allocated, whether sufficient page slots are allocated, etc.)

 

Multiprogramming level controls (whether the system is over-committed or under-committed, whether IEAOPTxx parameters should be adjusted, whether domain multiprogramming specifications should be adjusted, etc.)

 

Swap controls for preventable swaps (Exchange on Recommendation swaps, Unilateral swaps, Terminal Output Wait swaps, Detected Wait swaps, Improve System Paging Rate swaps, Improve Central Storage Usage swaps, and Make Room swaps)

 

Logical swapping controls (whether too much logical swapping occurred or whether logical swapping needs to be encouraged).

 

Expanded storage controls (whether expanded storage is being used effectively, whether ESCTxxxx keywords in IEAOPTxx need to be altered, etc.)

 

Coupling facility controls (CFRM parameters, structures, paths, etc.)
The MVS Component is normally executed each day, as a final step in the daily update of your performance data base.

The MVS Component analyzes standard SMF Type 70(series) data contained in your performance data base, and produces a narrative report for any measurement interval in which performance problems were detected. The report provides detailed information about the performance problems, identifies which parameters should be changed, and suggests new values which could be specified.

Sample output from the MVS Component.

The MVS Component User Manual provides a detailed description of each finding. The documentation includes an indication of what impact the finding would normally have, discusses why the finding was made (including a discussion of the MVS logic and operation involved), and suggests alternative ways to correct the potential problem. Most descriptions also contain specific references to IBM manuals or other documents relating to the finding.

Sample "rule" description from the MVS Component User Manual.

Users typically find that a number of problems are initially identified by CPExpert. These problems usually are resolved within a fairly short time. If the problems cannot be resolved (for example, because of "political" realities), the guidance provided to CPExpert usually is changed.

The result is that during normal day-to-day operation, the MVS Component should provide an indication of a problem only if the problem is "new" - that is, the system or workload changes and a new problem is encountered.

One example of such a "new" problem is the identification of impending shortage of page slots on page data sets. This problem might not exist initially.

However, with a changing (and perhaps increasing) workload, CPExpert might detect that the number of allocated page slots is insufficient to allow the Auxiliary Storage Manager's contiguous slot algorithm to be effective.

As another example, the MVS Component might detect that the Terminal Output Wait swap rate was too high, and TSOKEYxx parameters should be adjusted.

These subtle problems likely would not be detected by a normal performance analyst unless the analyst spent a considerable amount of time performing the boring calculations. The MVS Component would automatically provide an "alert" that a potential problem was arising.

The MVS Component provides a variety of processing options. For example, the options allow you (1) to select specific time periods or system identifications for analysis, (2) to override the default values which CPExpert uses to guide its analysis, and (3) to identify workloads which are critical versus those which have a relatively low priority.

The MVS Component of CPExpert is not applicable to MVS/Goal Mode. With Goal Mode, the functions of the MVS Component have been incorporated into the WLM Component of CPExpert.

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Last updated by Don Deese on 10/28/2004.