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DASD utility constraint relief (PJ48168)

By Mark Lehrer posted 7 days ago

  

Module copy (ZMCPY) and prime-duplicate comparison (ZMCMP) utilities use the main I-stream exclusively to do their work.  Multiple instances of these utilities can cause the main I-stream to be overloaded and impact other work. 

The following example illustrates this issue where a large number of active module comparisons are being processed. The ZDECB display of module comparison ECBs shows that all the comparison ECBs are running on the main I-stream: 

CSMP0097I 16.31.07 CPU-B SS-BSS  SSU-HPN  IS-01
DECB0014I 16.31.07 DISPLAY ECB SUMMARY
ECB ADDR  SSU IS  PGM     TRC MIN SC  ORIGIN   I H      DSP  SVC
14ED7000 HPN   1 CPDC    CPDC     20   1052    1          0 EHEAPC
14F1F000 HPN   1 CPDC    CPDC     19   1052    1          0 EHEAPC
14F31000 HPN   1 CPDC    CPDC     19   1052    1          0 EHEAPC
14F91000 HPN   1 CPDC    CPDC     19   1052    1          0 EHEAPC
14FB2000 HPN   1 CPDC    CPDC     19   1052    1          0 EHEAPC
14FE2000 HPN   1 CPDC    CPDC     19   1052    1          0 EHEAPC
15069000 HPN   1 CPDC    CPDC     18   1052    1          0 EHEAPC
15090000 HPN   1 CPDC    CPDC     18   1052    1          0 EHEAPC
150DE000 HPN   1 CPDC    CPDC     18   1052    1          0 EHEAPC
15117000 HPN   1 CPDC    CPDC     18   1052    2          0 EHEAPC
15171000 HPN   1 CPDC    CPDC     17   1052    1          0 EHEAPC
1518C000 HPN   1 CPDC    CPDC     17   1052    1          0 EHEAPC
1522E000 HPN   1 CPDC    CPDC     17   1052    1          0 EHEAPC
15264000 HPN   1 CPDC    CPDC     17   1052    1          0 EHEAPC
15294000 HPN   1 CPDC    CPDC     16   1052    1          0 EHEAPC
1533C000 HPN   1 CPDC    CPDC     16   1052    1          0 EHEAPC
15381000 HPN   1 CPDC    CPDC     16   1052    1          0 EHEAPC
153B1000 HPN   1 CPDC    CPDC     15   1052    1          0 EHEAPC
153F6000 HPN   1 CPDC    CPDC     15   1052    1          0 EHEAPC
1543B000 HPN   1 CPDC    CPDC     15   1052    1          0 EHEAPC
15474000 HPN   1 CPDC    CPDC     15   1052    1          0 EHEAPC
15480000 HPN   1 CPDC    CPDC     14   1052    1          0 EHEAPC
154D4000 HPN   1 CPDC    CPDC     14   1052    1          0 EHEAPC
15513000 HPN   1 CPDC    CPDC     14   1052    1          0 EHEAPC
1555B000 HPN   1 CPDC    CPDC     13   1052    1          0 EHEAPC
155BE000 HPN   1 CPDC    CPDC     13   1052    1          0 EHEAPC
155E8000 HPN   1 CPDC    CPDC     13   1052    1          0 EHEAPC
15621000 HPN   1 CPDC    CPDC     11   1052    1          0 EHEAPC
1564E000 HPN   1 CPDC    CPDC     12   1052    1          0 EHEAPC
156B1000 HPN   1 CPDC    CPDC     12   1052    1          0 EHEAPC
156F0000 HPN   1 CPDC    CPDC     12   1052    1          0 EHEAPC
15723000 HPN   1 CPDC    CPDC     12   1052    1          0 EHEAPC
15738000 HPN   1 CPDC    CPDC     11   1052    1          0 EHEAPC
157F5000 HPN   1 CPDC    CPDC     11   1052    1          0 EHEAPC
157FE000 HPN   1 CPDC    CPDC     11   1052    2          0 EHEAPC
15825000 HPN   1 CPDC    CPDC     11   1052    1          0 EHEAPC
15891000 HPN   1 CPDC    CPDC     10   1052    1          0 EHEAPC
158EB000 HPN   1 CPDC    CPDC     10   1052    1          0 EHEAPC
15909000 HPN   1 CPDC    CPDC      9   1052    1          0 EHEAPC
15975000 HPN   1 CPDC    CPDC      9   1052    1          0 EHEAPC
15996000 HPN   1 CPDC    CPDC      9   1052    1          0 EHEAPC
159C0000 HPN   1 CPDC    CPDC      9   1052    2          0 EHEAPC
TOTAL       42
END OF DISPLAY+

The following ZSTAT output shows that the ECBs are not evenly distributed between the I-streams and the utilization of the main I-stream is nearly 100%.

CSMP0097I 16.31.23 CPU-B SS-BSS  SSU-HPN  IS-01
STAT0039I 16.31.23 SYSTEM UTILIZATION DISPLAY
STATIC POWER SAVE MODE - SYSTEM AT 100 PERCENT
SPEED BOOST IS NOT ACTIVE
I-STREAM BOOST IS NOT ACTIVE
NUM  ADR  UTIL/ ADJ  CROSS READY INPUT   VCT SUSPD DEFER ACT-ECB S   PSU  LPUU
IS- 1 00  99.8/ 99.8     0     8     0     0     0    37     56  U   99.8 99.3
IS- 2 01    .2/   .2     0     0     0     0     0     0     12  U     .4   .3
IS- 3 02    .2/   .2     0     0     0     0     0     0     11  U    1.6  1.5
IS- 4 03    .2/   .2     0     0     0     0     0     0     12 CU     .3   .3
END OF DISPLAY+

If even more utility ECBs are started, the input list for the main I-stream might not be serviced in a timely fashion. 

CLHR0007W 12.39.44 THE INPUT LIST WAS NOT SERVICED IN THE LAST   2 SECONDS
NUM  ADR  UTIL/ ADJ  CROSS READY INPUT   VCT SUSPD DEFER ACT-ECB S   PSU  LPUU
IS- 1 00  99.8/ 99.8     3    75     2     1     0     0    123  U   99.8   .0
                 RLOG     IOB   FRAME  COMMON     SWB     XWB     ECB  FRM1MB
ALLOCATED      101120   12288   12000     500  501760 1000448    2000    3200
AVAILABLE      101119   12188   11990     326  501370  999525    1858    2621
END OF DISPLAY+

Changes were made to the module copy (ZMCPY) and prime-duplicate comparison (ZMCMP) utilities to use the switchable ECB attribute to help with workload distribution. Concurrent instances of module copy processing or prime-duplicate comparison utility processing can run across all in-use I-streams, which reduces main I-stream contention and the total time to complete all required instances.

A similar module comparison test was run with the same number of active module comparisons being processed. The ZDECB display of module comparison ECBs shows that the comparison ECBs are distributed across the in-use I-streams: 

CSMP0097I 11.28.32 CPU-B SS-BSS  SSU-HPN  IS-01
DECB0014I 11.28.32 DISPLAY ECB SUMMARY
ECB ADDR  SSU IS  PGM     TRC MIN SC  ORIGIN   I H      DSP  SVC
14F7A000 HPN   1 CPDC    CPDC   1 29   1052    2          0 EHEAPC 
14FDD000 HPN   2 CPDC    CPDC   1 27   1052    2          0 EHEAPC
1504C000 HPN   2 CPDC    CPDC   1 26   1052    1          0 EHEAPC
150A6000 HPN   4 CPDC    CPDC   1 25   1052    2          0 EHEAPC
150FD000 HPN   3 CPDC    CPDC   1 24   1052    1          0 EHEAPC
1517E000 HPN   1 CPDC    CPDC   1 22   1052    1          0 EHEAPC
151CC000 HPN   2 CPDC    CPDC   1 21   1052    2          0 EHEAPC
15226000 HPN   4 CPDC    CPDC   1 20   1052    2          0 EHEAPC
1529E000 HPN   3 CPDC    CPDC   1 18   1052    2          0 EHEAPC
152FE000 HPN   3 CPDC    CPDC   1 17   1052    1          0 EHEAPC
15349000 HPN   1 CPDC    CPDC   1 16   1052    2          0 EHEAPC
153B8000 HPN   4 CPDC    CPDC   1 14   1052    2          0 EHEAPC
1542A000 HPN   3 CPDC    CPDC   1 13   1052    1          0 EHEAPC
15478000 HPN   2 CPDC    CPDC   1 12   1052    1          0 EHEAPC
154D5000 HPN   3 CPDC    CPDC   1 10   1052    2          0 EHEAPC
15556000 HPN   4 CPDC    CPDC   1  9   1052    1          0 EHEAPC
155BC000 HPN   4 CPDC    CPDC   1  8   1052    1          0 EHEAPC
15616000 HPN   2 CPDC    CPDC   1  6   1052    2          0 EHEAPC
1568B000 HPN   4 CPDC    CPDC   1  5   1052               0 EHEAPC
156E8000 HPN   1 CPDC    CPDC   1  4   1052    1          0 EHEAPC
15754000 HPN   3 CPDC    CPDC   1  3   1052    2          0 EHEAPC
157C0000 HPN   1 CPDC    CPDC   1  1   1052    2          0 EHEAPC
1582C000 HPN   1 CPDC    CPDC   1  0   1052    1          0 EHEAPC
15880000 HPN   2 CPDC    CPDC     59   1052    2          0 EHEAPC
158FE000 HPN   4 CPDC    CPDC     57   1052    2          0 EHEAPC
15958000 HPN   1 CPDC    CPDC     56   1052    1          0 EHEAPC
159B8000 HPN   2 CPDC    CPDC     55   1052    2          0 EHEAPC
15A3C000 HPN   2 CPDC    CPDC     53   1052    2          0 EHEAPC
15A9C000 HPN   1 CPDC    CPDC     52   1052    2          0 EHEAPC
15AF0000 HPN   4 CPDC    CPDC     51   1052    2          0 EHEAPC
15B4A000 HPN   2 CPDC    CPDC     49   1052    1          0 EHEAPC
15BD1000 HPN   3 CPDC    CPDC     48   1052    2          0 EHEAPC
15C1F000 HPN   3 CPDC    CPDC     47   1052               0 EHEAPC
15C6A000 HPN   4 CPDC    CPDC     45   1052    2          0 EHEAPC
15CF4000 HPN   4 CPDC    CPDC     44   1052    2          0 EHEAPC
15D6F000 HPN   3 CPDC    CPDC     43   1052    2          0 EHEAPC
15DBD000 HPN   1 CPDC    CPDC     42   1052    1          0 EHEAPC
15E62000 HPN   2 CPDC    CPDC     40   1052    1          0 EHEAPC
15EC2000 HPN   3 CPDC    CPDC     39   1052    2          0 EHEAPC
15F85000 HPN   1 CPDC    CPDC     38   1052    1          0 EHEAPC
15FE8000 HPN   1 CPDC    CPDC     36   1052    2          0 EHEAPC
16048000 HPN   4 CPDC    CPDC     35   1052    2          0 EHEAPC
TOTAL       42
END OF DISPLAY+

The following ZSTAT output shows that the ECBs are more evenly distributed between the I-streams and the utilization of the main I-stream is more in line with the other I-streams: 

CSMP0097I 11.37.59 CPU-B SS-BSS  SSU-HPN  IS-01
STAT0039I 11.37.59 SYSTEM UTILIZATION DISPLAY
STATIC POWER SAVE MODE - SYSTEM AT 100 PERCENT
SPEED BOOST IS NOT ACTIVE
I-STREAM BOOST IS NOT ACTIVE
NUM  ADR  UTIL/ ADJ  CROSS READY INPUT   VCT SUSPD DEFER ACT-ECB S   PSU  LPUU
IS- 1 00  41.1/ 41.1     0    12     0     0     0     1     23  U   41.6 41.1
IS- 2 01  41.8/ 41.8     0     0     0     0     0     0     20  U   43.9 43.8
IS- 3 02  42.2/ 42.2     0     0     0     0     0     0     21  U   42.4 42.4
IS- 4 03  40.2/ 40.2     0     0     0     0     0     0     21 CU   41.4 41.4
END OF DISPLAY+

To prevent possible performance issues because of contention to update memory locations, each copy control record entry is placed in its own cache line aligned storage. This change applies only to the copy control record in memory. The copy control record on file will occupy the same space in the BSS keypoint V (CTKV) that it did before this APAR. 

For more information about APAR PJ48168, see the APEDIT. 

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