# DASD Group Volume Performance

The DASD Group Volume Performance attributes provide information about the volumes and associated metrics that are in the DASD Group Volume Performance workspace.

Average Command Response Delay: The average number of milliseconds that a successfully initiated start or resume function needs until the first command is indicated as accepted by the device over the RMF interval.

Average HyperPAV Alias Count: The average number of alias devices assigned to a base volume in a HyperPAV environment over the RMF interval.

Busy Percent: The percentage of time a resource is busy processing I/O requests. For Parallel Access Volumes, this value is normalized by dividing by the number of PAV exposures.

Channels: The Channel Path IDs (in hexadecimal) through which this device may be accessed.

CHPID SEL: The CHPID selector is used as an index to limit the range of physical volumes for which data is requested.

Connect Time: The average time required for seek and transfer. This is the time it takes for data to be located on the track and transferred between the DASD device and central storage.

Control Unit Busy Delay Time: The average amount of I/O delay (in milliseconds) to this device caused by a control unit busy condition. This is the time it takes for data to be located on the track and transferred between the DASD device and central storage.

CU Model: The model indicator for this cache control unit.

Current PAV Exposures: The current number of UCBs through which the device may be accessed.

DCBs Open: The number of open datasets on this device.

Device Address: Four hexadecimal digits that define the physical address of this device. Also known as unit or unit address.

Device Busy Delay Time: The average amount of I/O delay (in milliseconds) to this device caused by a device busy condition.

Device Hex Address: The device address (in hexadecimal).

Device Model: The model of the DASD device.

Device MPL: The device multi-processing level, which is the I/O density for a device. This metric is the product of the millisecond response time (MSR) and I/O rate per second for the device. For a PAV volume, this value is normalized by dividing by the number of exposures.

Device Type: The MVS device type (derived from UCBTBYT4).

Director Busy Delay Time: The average amount of I/O delay (in milliseconds) to this device caused by a director port busy condition.

Disconnect Time: The average time, in milliseconds that I/O waited because the device was not connected to the channel. This time includes moving the device to the requested cylinder, waiting for the record to rotate under the head (rotational delay), and waiting for the channel to become available.

I/O Count: The actual number of I/O requests issued for this device during this interval.

I/O Per Second: The average number of I/O operations per second.

IOSQ Delay: The average time that an I/O waits because the device is already busy. A device is determined to be busy if its UCBBUSY bit is on.

LCU Number: The logical control unit number.

LCU Number Hex: The logical control unit number for this device (hexadecimal).

Managed System: An internal node name used to identify the system from which this row of data was obtained.

Maximum PAV Exposures: The maximum number of UCBs through which the device could be accessed.

MSR Connect Time Percent: The percentage of the device response time during which the device was connected. This value is obtained be dividing the device pending time by the total millisecond response time.

MVS Status: The status of this device in the local MVS system.

PAV Exposure Changed: Indicates whether the number of PAV exposures for the volume has changed over the interval.

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

Physical Device: The type of physical device containing this logical device.

RAID Model: The RAID type indicator (Symmetrix, Iceberg, RAMAC OR 2105).

Reserved Percent: The percentage of time during the interval when a shared device was reserved by this system.

Response Time: The total hardware service time and the front end software queuing time involved for the average I/O request to the device.

SMS Conversion Status: The SMS conversion status of this volume (non-SMS, initial, converted, or excluded).

SMS Status: The SMS volume status for local system (enabled, quiesced_all, quiesced_new, disabled_all, or disabled_new).

Solid State Device: An indication of whether the logical volume is backed by a solid state physical device.

Storage Group Name: The name of the SMS storage group to which this volume belongs.

Subsystem ID Index: A two-byte unique value used to identify a 3990 or equivalent storage control unit.

Time Stamp: The date and time this data was reported. Primarily for use in historical reporting.

User Group Name: The user-assigned name for a group of DASD volumes.

Volume: This is the volume serial number of a disk device currently in use by this application.

VTOC Index Status: The type of VTOC present on this device.