File Statistics

File Statistics identifies some response time statistics for data sets. Values are in microseconds.

  • RESP displays the average I/O response time. Examining this value in conjunction with the value reported in the MSR field provides a method of determining the cache usage of the data set. Generally, an average response time lower than 25 indicates that the data set was cached.
  • PEND displays the average pending time. This value represents the average amount of time spent waiting to connect to a device.
  • IOSQ displays the average I/O Supervisor queue time. This value represents the average time spent waiting for service during an I/O operation while the device was busy with an operation from another system.
  • DISC displays the average disconnect time. This value represents the average time that the device on which the data set resides was logically disconnected from the channel subsystem. A low average disconnect time usually indicates that the data set has a good hit ratio.

Tip

High values in the IOSQ, PEND, and DISC fields may indicate that other data sets on this volume or 3390 string are caching poorly. That which constitutes a high value is determined by your site’s service level objectives. For example, the service level objective for a particular DASD volume’s response time could be 10 milliseconds. If a data set on that volume has an average response time of 25 milliseconds, that data set might be considered to have a high response time and would warrant investigation.

More about the Data-Set-Characteristics report.

 

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