Cache Subsystem Activity Report

SUBSYSTEM ID

Physical control unit number of the cache subsystem

MODEL

Hardware model ID

Control UNIT

Physical control unit number of the caching subsystem; this number is equal to the lowest device number for the subsystem

MFR

Manufacturer code of the cache subsystem

PLANT

Plant code of the cache subsystem

SERIAL

Serial number of the cache subsystem

SUBSYSTEM STORAGE

Cache storage status, in megabytes:

• CONFIGURED—amount installed
• AVAILABLE—amount available
• PINNED—amount pinned in cache - DASD failure prevents data destaging
• OFFLINE—amount offline, possibly due to error

NON-VOLATILE STORAGE

Nonvolatile storage (NVS) status, in megabytes:

• CONFIGURED—amount installed
• PINNED—amount pinned in NVS - DASD failure prevents data destaging

SUBSYSTEM STATUS

Caching status of the entire subsystem:

CACHING

• ACTIVE—caching online and usable
• PENDING ACTIVE—cache being brought online
• INTERNAL ERROR—internal error stopped caching
• HOST TERMINATION—host deactivated caching
• CACHE SUSPENDED—caching suspended
• PENDING OFFLINE—cache deactivation is pending
• PENDING OFF FAIL—cache deactivation failed
• IN MAINTENANCE—cache disabled for maintenance
• ?????—unknown status

NON-VOLATILE STORAGE

• ACTIVE—NVS caching is online and usable
• INTERNAL ERROR—internal error stopped NVS cache
• HOST TERMINATION—host deactivated NVS caching
• DFW SUSPENDED—DFW inhibited - battery failure
• PENDING OFFLINE—NVS cache deactivation pending
• IN MAINTENANCE—NVS disabled for maintenance
• ?????—unknown status

CACHE FAST WRITE

• ACTIVE—CFW is active
• DEACTIVATED—CFW has been deactivated

IML DEVICE AVAILABLE

• YES—IML device is operational
• NO—IML device is not operational

I/O TOTALS

Number of I/O requests:

• CACHE—cacheable I/O requests to cached devices
• OFFLINE—I/O requests to non-cached devices
• NONCACHE—sum of INHIBIT CACHE LOAD and CACHE BYPASS requests
• TOTAL—sum of all I/O requests

HIT %

Cache hits, as percentages of all I/O requests:

• CACHE—percentage of cacheable I/O requests that were serviced from cache
• TOTAL—percentage of all I/O requests that were serviced from cache

CACHE I/O REQUESTS

Specified by the DEFINE EXTENT command; categorizes the way cache is managed, as one of three classes:

• NORMAL—use the normal LRU algorithm to make cache space available
• SEQUENTIAL—preload of tracks from DASD for sequential I/O requests
• CFW DATA—handle WRITE and READ-AFTER-WRITE requests in cache
• TOTAL—totals or averages for the three defined classes

READ I/O REQUESTS

I/O requests that had at least one SEARCH or READ command and no WRITE command; only requests to cached devices are counted:

• COUNT—total number of SEARCH/READ requests
• RATE—SEARCH/READ requests per second
• HITS—SEARCH/READ requests handled without accessing DASD
• RATE—SEARCH/READ requests handled without accessing DASD, per second
• HIT %—SEARCH/READ cache hits, as a percentage of all such requests

WRITE I/O REQUESTS

I/O requests that had at least one WRITE command; only requests to cached devices are counted:

• COUNT—total number of WRITE requests
• RATE—WRITE requests per second
• FAST—CACHE/DASD FAST WRITE (CFW and DFW) requests
• RATE—CFW/DFW requests per second
• HITS—CFW/DFW requests handled without accessing DASD
• RATE—CFW/DFW requests processed without accessing DASD, per second
• HIT %—CFW/DFW cache hits, as a percentage of all WRITE requests

% READ

READ requests as a percentage of all READ and WRITE requests

CACHE MISSES

Occurs under the following situations:

• Data to be read or written is not found in the cache. This problem causes the track or tracks containing the data to be read from DASD and placed in the cache.
• A lack of NVS storage causes the data to be written to DASD immediately.
• For some reason, DASD FAST WRITE (DFW) is inhibited.

Possible values are:

• READ—SEARCH/READ requests that accessed DASD
• RATE—SEARCH/READ requests that accessed DASD, per second
• WRITE—WRITE requests that accessed DASD
• RATE—WRITE requests that accessed DASD, per second
• TRACKS—number of tracks transferred from DASD to cache
• RATE—number of tracks transferred from DASD to cache, per second

MISC

Miscellaneous I/O requests

DFW BYPASS

Number of DASD FAST WRITE (DFW) requests that might have been written to NVS, except that NVS was over-committed. This situation forced the writes to be sent directly to DASD.

• COUNT—total number of DFW BYPASS requests
• RATE—DFW BYPASS requests per second

CFW BYPASS

Number of I/O requests with the CACHE FAST WRITE (CFW) attribute that went directly to DASD because the cache was full. No waiting for destaging is done for these requests.

• COUNT—total number of CFW BYPASS requests
• RATE—CFW BYPASS requests per second

DFW INHIBIT

If DASD FAST WRITE (DFW) is active, the number of WRITE requests that inhibited DFW. If DFW is inactive, the number of WRITE requests that directly accessed the DASD is recorded in this field.

• COUNT—total number of DFW INHIBIT requests
• RATE—DFW INHIBIT requests per second

ASYNC (TRKS)

Number of tracks asynchronously transferred from cache to DASD, in order to free space in the cache and the NVS. For a duplex pair, this figure is the number of transfers from the primary cache to the secondary. A high number of ASYNC I/Os indicates an over-committed cache or NVS.

• COUNT—number of tracks asynchronously transferred from cache to DASD
• RATE—number of tracks asynchronously transferred, per second

NON-CACHE I/O

I/O requests that bypass the cache

ICL

Inhibit cache load (ICL)

Number of I/O requests that inhibited the loading of data into cache, even though the data was not found in the cache.

• COUNT—total number of ICL requests
• RATE—ICL requests per second

BYPASS

Number of I/O requests that explicitly bypassed the cache, whether or not the data was in the cache:

• COUNT—total number of BYPASS requests
• RATE—BYPASS requests per second

TOTAL

Total number of I/O requests that bypassed the cache:

• COUNT—number of I/O requests that bypassed the cache
• RATE—number of I/O requests that bypassed the cache, per second

TOTAL CACHE MISSES

Count and rate of I/O requests that were not serviced from cache

TOTAL CACHE HITS

Count and rate of I/O requests that were serviced from cache

SYNCH I/O ACTIVITY

(PTF BQM1573 applied)

DISK ACTIVITY

Transfer activity from hard disk to cache and vice versa. This information is available only for 2107 and 1750 subsystems; for all other subsystems, dashes will print in place of the missing data.

HOST ADAPTER ACTIVITY

I/O activity of normal, sequential, and CFW read and write requests. This information is available only for 2107 and 1750 subsystems; for all other subsystems, dashes will print in place of the missing data.

RESP TIME

Response time in milliseconds per read and write request

BYTES/REQ

Average number of bytes transferred per read and write requests

BYTES/SEC

Average number of bytes transferred per second per read and write requests

CKD STATISTICS

Count-Key-Data (CKD) track format requests:

• WRITE—number of CKD WRITE requests (also in total WRITE count)
• WRITE HITS—CKD WRITE requests that were handled in cache

RECORD CACHING

Dynamic record caching counts; normally, only whole tracks are cached:

• READ MISSES—count of records to be read that were not in the cache
• WRITE PROM—count of records to be written that needed to access DASD

DEV NUM

Five-digit device number that uniquely identifies the DASD device

VOLUME SERIAL

Volume serial number

XTNT POOL or

RRID

ID of the extent pool to which the device belongs (for 2107s and 1750s only)

RAID rank identifier (for systems other than 2107s and 1750s)

STATUS

Cache status of the DASD device:

• CACHE—caching status
• DASDFW—DASD Fast Write (DFW) status

% I/O

I/O requests to this DASD volume, as a percentage of all I/O requests to the cache subsystem to which it belongs

I/O RATE

I/O requests per second to the volume

CACHE HIT RATE

I/O requests per second that completed without accessing DASD, by request type:

• READ—number of READ requests
• DFW—number of DFW (DASD Fast Write) requests
• CFW—number of CFW (Cache Fast Write) requests

DASD I/O RATE

I/O requests per second that accessed DASD, by request type:

• STAGE—normal or sequential requests
• DFWBP—requests that caused DFW to be bypassed
• ICL—ICL (Inhibit Cache Load) requests
• BYP—requests that explicitly bypassed the cache
• OTHER—requests that were either CFW BYPASS or DFW INHIBIT requests

ASYNC RATE

Number of tracks asynchronously written to the DASD device in order to release space in the cache or NVS storage. A high rate indicates that storage might be over-committed.

% HITS

I/O requests serviced from the cache, as percentages of all I/O requests

TOTAL

Percentage of READ and WRITE requests that were serviced from the cache

READ

Percentage of READ requests that were serviced from the cache

WRITE

Percentage of WRITE requests that were serviced from the cache

READ

READ requests as a percentage of all I/O requests

ID

RAID rank identifier

TYPE

RAID rank type

DA

Device adapter identifier

HDD

Number of hard disk drives (HDD) in the RAID rank

READ REQUESTS

READ I/O requests:

• COUNT—number of READ requests
• RATE—number of READ requests, per second
• AVG SZ—average number of bytes transferred per READ request
• BYTE/S—average number of bytes read, per second
• RTIME—average response time, in milliseconds, to an HDD READ I/O request

WRITE REQUESTS

WRITE I/O requests:

• COUNT—number of WRITE requests
• RATE—number of WRITE requests, per second
• AVG SZ—average number of bytes that were transferred per WRITE request
• BYTE/S—average number of bytes that were written, per second
• RTIME—average response time, in milliseconds, to an HDD WRITE I/O request

HIGHEST ACTIVITY VOLUMES

Top five volumes sorted in descending order by I/O activity