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.

Hint: 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