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Method and Apparatus to Monitor PAV Utilization Disclosure Number: IPCOM000082878D
Original Publication Date: 2005-Feb-28
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 58K

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The PAV Analysis tool is invented to help the *IBM *zSeries customers understand the Parallel Access Volume (PAV) Device Alias utilizations in both a static PAV environment and a dynamic environment where the *z/OS Work Load Manager manages PAV-alias to PAV-base relationships. With this PAV alias utilization customers can determine the right ratio of PAV-base devices to PAV-alias devices can be determined for the given customer work load. An excessive ratio of PAV-aliases to PAV-bases severly limits the amount of data that can be addressed, placing additional pressure on the 64K device number limit. Too small a ratio results in growing IOS queue time, impacting the response time and possibly causing the customer's work load to not meet the business goals.

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Method and Apparatus to Monitor PAV Utilization

The design for PAV-alias device usage is to keep the same PAV-alias devices the busiest, even after they are dynamically moved. This is done by scanning the PAV-alias device queue in the same order and always selecting the first free PAV-alias to start the new I/O request. The PAV-aliases devices at the front of the queue will tend to stay the busiest. When ever WLM decides to use a PAV-base device as an alias donor, it requests IOS to move an alias. The I/O supervisor always selects the first (busiest) PAV-alias. When PAV-alias moves to the target logical volume, it is always queued as the first alias to the target device, Thus, the same PAV-alais will stay as the busiest alias to the target device. The individual PAV alias utilizations are captured for each n second interval, where n is specified by the customer. The data is written to a sequential data set for post processing by the analysis tool. The PAV analysis tool accepts as input sequential dataset that contains all the individual alias utilizationover time. The tool sums it up over all the time intervals then display the utilization per time interval in the 3 dimensional graph, busiest device to least busiest device. From the display the user can see if any of the aliases are idle over the total interval. If so, the customer canreduce the number of PAV-aliases defined without impacting the I/O respoonse time of the workload.


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PAV Analysis Tool...