# DASD Physical Group

The DASD Physical Group attributes provide performance information for a physical volume group. A physical volume group is the set of logical volumes that are related by a hardware specific construct.

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 aliased 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 PAV volumes, this value is normalized by dividing the number of PAV exposures.

Bypass Cache Percentage: The percentage of I/Os that bypassed cache this interval. The I/O request is sent directly to DASD. Tracks are neither read from cache nor promoted to cache. Also, their entries in the LRU list are not updated.

Cache FW % Read: The percentage of all I/Os that were read operations for data in cache that originated from a cache fast write during this interval. Cache fast write is a form of fast write where the data is written directly to cache without using nonvolatile storage and is available for later destaging.

Cache FW % Write: The percentage of all I/Os that were cache fast writes during this interval. Cache fast write is a form of fast write where the data is written directly to cache without using nonvolatile storage and is available for later destaging.

Cache Status: The caching status for this volume. Active means caching for this volume is active and inactive means caching for this volume is inactive.

Cache to DASD Total Tracks: The number of tracks written from cache to physical disk during the cache interval. This value is captured asynchronously with respect to the transfer of data from the channel to the cache.

Cache to DASD Tracks per Sec: The rate per second of tracks written from cache to physical disk during the cache interval. This value is captured asynchronously with respect to the transfer of data from the channel to the cache.

Connect Time: Part of I/O during which data is located on the track and transferred between the DASD device and central storage.

Control Unit Model: The model number associated with the control unit to which this device is attached.

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

DASD to Cache Non Promotes Second: The rate per second of operations that did not promote (copy) a track to cache because free cache segments were not available.

DASD to Cache Non-promotes: The number of operations that did not promote (copy) a track to cache because free cache segments were not available.

DASD to Cache Total Tracks Non-sequential: The number of tracks read from physical disk to cache over the cache interval for non-sequential I/O operations.

DASD to Cache Total Tracks Sequential: The number of tracks read from physical disk to cache over the cache interval for sequential I/O operations.

DASD to Cache Total Tracks: The number of tracks read from physical disk to cache over the cache interval for I/O operations.

DASD to Cache Tracks per Sec Non-sequential: The rate per second of tracks read from physical disk to cache over the cache interval for non-sequential I/O operations.

DASD to Cache Tracks per Sec Sequential: The rate per second of tracks read from physical disk to cache over the cache interval for sequential I/O operations.

DASD to Cache Tracks per Sec: The rate per second of tracks read from physical disk to cache over the cache interval for I/O operations.

DCBs Open: The count of open data sets.

Device Address: The MVS™ device number assigned by HCD and associated with this device.

Device MPL: The device multi-processing level, which is the I/O density for a device. This metric is the product of the MSR (millisecond response time) and I/O per second for a device.

DFW Hit Percent: The percentage of all DASD I/Os to this volume that were DASD fast writes during this interval. DASD fast write is a form of fast write to cache where the data is written concurrently to cache and nonvolatile storage and automatically scheduled for destaging to DASD.

DFW Retry Percent: The percentage of DASD I/O operations that required retry during this interval.

DFW Status: The status of the DASD fast write option for this volume. Value can be Active, Inactive, Unknown or Timeout.

Disconnect Time: The time that I/O spends, free from the channel searching for or requesting data.

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.

Inhibit Cache Percent: The percentage of I/O operations that inhibited the loading of data into cache. If the data is already in cache, the request is satisfied from cache.

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 Contention Rate: The average number of requests delayed due to LCU contention. LCU contention is the rate per second at which the SAP places delayed I/O requests on the CU-HDR for this LCU. This calculation is performed when all paths to the subchannel are busy and at least one path to the control unit is busy. For devices with only one path, or devices where multiple paths exist and the busy condition is immediately resolved, the IOP does not count the condition.

LCU Number: The three hexadecimal digit logical control unit number.

Managed System: The SMS name of this system.

Maximum PAV Exposures: The maximum number of UCBs through which the device can be accessed in this interval.

MSR Connect Time Percent: The percentage of MSR (millisecond response time) during which data is transferred (SEARCH + TRANSFER).

PAV Exposure Changed: Indicates that the number of PAV exposures to this device changed during this interval.

Pend Time: The time 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 Hit Percent: The percentage of read hits for this volume.

Read I/O Count: The number of read operations directed to this device that completed during this interval.

Read I/O Percent: The percentage of I/O requests to this volume that were read requests.

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

Response Time: The amount of time in milliseconds it takes for an I/O request to complete to a given device. MSR (millisecond response time) is divided into four components: IOS Queue, Pending, Disconnect and Connect.

Selected Volser: The volume serial number associated with the physical volume selected for display.

SMS Status: The SMS volume status for the local system. Values are: Enabled, Quiesced_All, Quiesced_New, Disabled_All or Disabled_New.

Storage Group Name: The 32-character name of the SMS storage group to which this volume belongs.

Subsystem ID: The MVS identifier of the logical control unit to which this device is attached.

Volume: The VOLSER associated with this physical volume.

VTOC Index Status: The status of the VTOC index on this volume. Values are Enabled, Disabled, Error, OS_VTOC or Excluded.

Write Hit Percent: The percentage of I/O operations that completed without accessing the hard disk drive.

Write I/O Count: The number of write operations directed to this device that completed during this interval.