12.2.1.4Cache Subsystem Activity Reports Analysis These reports address questions:

1.Is cache overloaded ?

2.What is the efficiency of staging and destaging processes ?

All %READ fields of reports show 100%, so the I/O activity is read-only.

Focus the analysis on LCU 0046, associated with the CU-ID 2B00; refer to Figure 71 on page 151. In the cache subsystem device overview report, the I/O RATE from the host is 18.2, of which 18.0 are reads and READ H/R is 0.991, which is good. Moreover, in the CACHE MISSES subset of the CACHE SUBSYSTEM OVERVIEW, the SEQUENTIAL LINE shows 93457 tracks staged for sequential prefetch at a rate of 41.1 per second between disk and cache. Those figures describe well the cache behaviour: intensive sequential read demand, satisfied by an intensive pre-staging activity with a good hit ratio. The disconnect time

observed in the device activity report comes from a probable sustained host demand slightly faster than pre-staging.

This observation can be done on almost every RVA LCU. The CU-ID 2BC0 and 2CC0 show missing data because of a probable operator setting during the test; IXFP reports should complement it.

 

 

 

C A C H E S U B S Y S T E M A C T I V I T Y

 

SUBSYSTEM

3990-03

CU-ID 2B00

SSID 0088

CDATE 02/12/1999

CTIME 15.05.40

CINT 00.37.56

TYPE-MODEL

9393-002

 

 

 

 

 

 

 

 

 

(RMF report extract)

 

 

------------------------------------------------------------------------------------------------------------------------------------

CACHE SUBSYSTEM OVERVIEW

------------------------------------------------------------------------------------------------------------------------------------

TOTAL I/O

41324

CACHE I/O

41324

CACHE OFFLINE

0

 

 

 

 

 

 

 

 

TOTAL H/R

0.991

CACHE H/R

0.991

 

 

 

 

 

 

 

 

 

 

 

 

CACHE I/O

-------------

READ I/O REQUESTS-------------

 

----------------------WRITE I/O REQUESTS----------------------

 

 

%

REQUESTS

COUNT

RATE

HITS

 

RATE

H/R

COUNT

RATE

FAST

RATE

HITS

RATE

H/R

READ

NORMAL

892

0.4

 

547

 

0.2

0.613

0

0.0

0

 

0.0

0

0.0

N/A

100.0

SEQUENTIAL

40432

17.8

40392

 

17.7

0.999

0

0.0

0

 

0.0

0

0.0

N/A

100.0

CFW DATA

0

0.0

 

0

 

0.0

N/A

0

0.0

0

 

0.0

0

0.0

N/A

N/A

TOTAL

41324

18.2

40939

 

18.0

0.991

0

0.0

0

 

0.0

0

0.0

N/A

100.0

------------------------

CACHE MISSES-----------------------

 

 

 

 

------------MISC------------

 

 

------NON-CACHE I/O-----

REQUESTS

READ

RATE WRITE

RATE

TRACKS

RATE

 

 

COUNT

RATE

 

 

COUNT

RATE

 

 

 

 

 

 

 

 

 

DFW BYPASS

 

0

0.0

 

ICL

0

0.0

NORMAL

345

0.2

0

0.0

385

0.2

 

CFW BYPASS

 

0

0.0

 

BYPASS

0

0.0

SEQUENTIAL

40

0.0

0

0.0

93457

41.1

 

DFW INHIBIT

 

0

0.0

 

TOTAL

0

0.0

CFW DATA

0

0.0

0

0.0

 

 

 

ASYNC (TRKS)

0

0.0

 

 

 

 

TOTAL

385

RATE

0.2

 

 

 

 

 

 

 

 

 

 

 

 

 

----CKD STATISTICS---

---RECORD CACHING---

 

 

 

 

 

 

 

 

 

 

WRITE

0

READ MISSES

 

0

 

 

 

 

 

 

 

 

 

 

WRITE HITS

0

WRITE PROM

 

 

0

 

 

 

 

 

 

 

 

 

 

-----------------------------------------------------------------------------------------------------------------------------------

CACHE SUBSYSTEM DEVICE OVERVIEW

-----------------------------------------------------------------------------------------------------------------------------------

VOLUME

DEV

DUAL

%

I/O

---CACHE HIT RATE--

----------DASD I/O RATE----------

 

ASYNC

TOTAL

READ

WRITE

%

SERIAL

NUM

COPY

I/O

RATE

READ

DFW

CFW

STAGE

DFWBP

ICL

BYP

OTHER

RATE

H/R

H/R

H/R

READ

*ALL

 

 

100.0

18.2

18.0

0.0

0.0

0.2

0.0

0.0

0.0

0.0

0.0

0.991

0.991

N/A

100.0

*

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 71. Case Study RMF Cache Subsystem Activity Extracts

Case Study 151

Page 173
Image 173
IBM 5695-DF1, 5655-DB2 manual Case Study RMF Cache Subsystem Activity Extracts

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