# Dataset Performance

The Dataset Performance attributes provide performance information for a data set by application or summarized for all applications accessing the data set. They provide metrics at the I/O component level.

ASID: The address space ID of the job using this data set.

Cache Hit Percent: The sum of cache read hits plus cache write hits divided by the sum of cache-eligible reads plus cache-eligible writes.

Cache Read Hit Percent: The number of cache read hits divided by cache-eligible reads.

Cache Write Hit Percent: The number of cache write hits divided by the number of cache-eligible writes.

Connect Time Percent: The ratio of connect time divided by MSR (millisecond response time), expressed as a percentage.

Connect Time: Represents time in milliseconds spent locating data on the track and transferring between the DASD device and central storage.

Dataset Name: The MVS™ data set name.

Device Active Only Percent: The average device active only time per I/O in milliseconds.

Device Active Only Time: That portion in milliseconds of total MSR (millisecond response time) that occurs after 'CHANNEL-END' but before 'DEVICE-END'.

Device Address: The MVS device number, assigned by HCD, associated with the device on which the data set is located.

Disconnect Time Percent: The ratio of disconnect time divided by MSR (millisecond response time), expressed as a percentage.

Eligible Cache Percent: The percentage of total I/Os that were cache eligible.

Total I/O Count: The total number of I/Os (read and write) processed for the data set.

I/O Per Second: The average number of I/O operations per second for this data set during this interval.

IOSQ Time Percent: The ratio of IOSQ time divided by MSR (millisecond response time), expressed as a percentage.

IOSQ Time: The average time in milliseconds that an I/O waits because the device is already busy (signified by the UCBBUSY bit for a device being on).

JOB_START: Job Start value.

Jobname: The MVS JOBNAME that is using this data set.

Low SC Objective: The lower value of direct or sequential storage class MSR (millisecond response time) objective.

Managed System: The SMS name of this system.

NON_C_READ: Non C Read value.

NON_C_WRIT: Non C Writ value.

Pend Time Percent: The ratio of pending time divided by MSR (millisecond response time), expressed as a percentage.

Pend Time: The time in milliseconds that I/O is delayed in the path to the device. Pending time can be attributable to the channel or control unit path being busy.

Read Disconnect Time: The average time in milliseconds that read I/O waits because the device is not connected to the channel.

Read I/O Count: Total number of read I/Os processed for the data set.

Read Write Percent: The sum of cache-eligible reads plus non-cache reads divided by the total I/O.

Response Time Index: The total response time in milliseconds for this data set during this interval.

Response Time: The total millisecond response time for this data set during this interval.

SC Direct MSR Objective: The target direct response time specified for this storage class. This value is used during allocation to select a volume with acceptable performance characteristics. This value also influences caching.

SC Sequential MSR Objective: A construct in the SMS storage class that is used during allocation and indicates the desired response time for sequential accesses to this data set.

Storage Class Name: The name of the SMS storage class to which this data set belongs.

Time Stamp: The date and time used to control the scope of the query.

Total Disconnect Time: The average time in milliseconds that all I/O (read and write) waits because the device is not connected to the channel.

Volume: The six-character name of the DASD volume where this data set is located.

Write I/O Count: Total number of write I/Os processed for the data set.

Write Disconnect Time: The average time in milliseconds that write I/O waits because the device is not connected to the channel.