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138 Storage Management with DB2 for OS/390
• WRITE PER SEC is the average number of write operations per second for
the subsystem.
• I/O PER SEC is the average number of I/O operations per second for the
subsystem. This field may not be equal to the sum of READ PER SEC and
WRITE PER SEC, either because it includes other I/O operations, such as
sense commands, or because there may be more than one read or write
operation per channel program. Accounting of I/O per second is based on
number of Locate Record CCWs met in the channel programs.
• READ HIT% is the percentage of read operations for which the referred track
was present in cache storage.
• WRITE HIT % is the percentage of write operations for which the referred
track was present in cache storage.
• STAGE PER SEC is the number of transfers of tracks of data from DASD
storage to cache storage per second.
• HITS / STGE is the ratio of cache hits (in number of I/Os) to cache misses
(in number of staged tracks).
Figure 55. IXFP Cache Effectiveness Subsystem Summary Report
11.3.3 Space Utilization Report
Figure 56 on page 139 shows the subsystem space utilization summary report.
This information is mainly storage business oriented, but high net capacity load
(NCL) ratios may trigger more intensive RVA background garbage collection
processes, which can impact overall performance. Moreover, low compression
ratios involve higher activity between cache and disk. An RVA is considered as
balanced with a 3.6 compression ratio and with an NCL lower than 75%.
IBM ITSO POKEEPSIE 17:30 Thursday, February 18,
XSA/REPORTER CACHE EFFECTIVENESS OVERALL SUMMARY 18FEB1999 17:32:04
SIBCEIO V2 R1 L1
REPORT START DATE: 17FEB1999 REPORT END DATE: 17FEB1999
REPORT START TIME: 15:16 REPORT END TIME: 15:54
SUBSYSTEM NAME: 20395 (CACHE SIZE: 1024 MB NVS SIZE: 8 MB)
FDID DEV VOLSER T/P READ WRITE I/O READ READ WRITE I/O DFW STAGE HITS/ LOW
ADDR PER SEC PER SEC PER SEC RATIO HIT % HIT % HIT % CONSTR PER SEC STGE REF CT
---- ---- -------- --- ------- ------- ------- ----- ----- ----- ----- ------ ------- ----- ------
0000 2B00 RV2B00 P 4.9 0.0 4.2 11077 100.0 100.0 100.0 0.00 11.2 0.4 76.4
0001 2B01 RV2B01 P 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00 0.0 0.0 0.0
0002 2B02 RV2B02 P 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00 0.0 0.0 0.0
00FE 2BFE RV2BFE P 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00 0.0 0.0 0.0
00FF 2BFF RV2BFF P 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.00 0.0 0.0 0.0
SUBSYSTEM READ WRITE I/O READ READ WRITE I/O DFW STAGE HITS/ LOW TRACK
SUMMARY PER SEC PER SEC PER SEC RATIO HIT % HIT % HIT % CONSTR PER SEC STGE REF CT OCCUP
------- ------- ------- ----- ----- ----- ----- ------ ------- ----- ------ ------
PROD PARTITION 53.8 0.0 45.7 61329 99.3 100.0 99.3 0.0 113.2 0.5 73.7
OVERALL TOTALS 53.8 0.0 45.7 61329 99.3 100.0 99.3 0.0 113.2 0.5 73.7 25050