I have a customer with what they perceive as a memory problem, Reviewing
their JCL I feel otherwise. There are some VSAM BLSR values that I
seriously question. I have written a response but am now having insecurity
issues - its been a while and although "VSAM Demystified" and "DFSMS Using
Data Sets" seem to confirm most of my material, I'd sure like to see a z/OS
R1.9 VSAM PLM for a few hours.
I have my beach towel handy in case the egg on my face get real deep.
Comments and pointers appreciated.
Cut/Paste
90 XXH99NMODF DD SUBSYS=('BLSR','DDNAME=BLSRMODF', *MOD FILE *
XX 'BUFSI=4096,BUFSD=8192',
CISIZES --------------1536 ------4096
DATA CI/CA----------------180
KEYLEN---------------------14
XX 'BUFNI=7972,BUFND=272',
XX 'RMODE31=ALL','MSG=I',
XX 'SHRPOOL=01')
91 XXBLSRMODF DD DSN=&V1..HBBMA.YW&PL.MODS, * MODIFIER FILE *
XX DISP=(SHR,KEEP,KEEP)
IEFC653I SUBSTITUTION JCL - [email protected],DISP=(
92 XXH99NPFLG DD SUBSYS=('BLSR','DDNAME=BLSRPFLG', *PFLG FILE *
XX 'BUFSI=4096,BUFSD=8192',
CISIZES --------------1536 ------4096
DATA CI/CA----------------180
KEYLEN-----------------8
XX 'BUFNI=4070,BUFND=532',
XX 'RMODE31=ALL','MSG=I',
XX 'SHRPOOL=01')
93 XXBLSRPFLG DD DSN=&V1..HBBMA.MW&PL.PFLG&NODE, *PROC STUB FILE*
XX DISP=(SHR,KEEP,KEEP)
IEFC653I SUBSTITUTION JCL - [email protected],DISP=(
Note that the JCL above is TEST and that the files are small but the values
are intended for PROD volumes.
Since the two data sets are the only ones that have SHRPOOL=01 we consider
them together as a start. All the others default to SHRPOOL=0.
As they are both have INDEX ----1536 and DATA ---4096 CISIZES, I do not
understand the use of 'BUFSI=4096,BUFSD=8192'. It would seem that
(4096 - 1536) = 2560 bytes = 62% of each INDEX and
(8192 - 4096) = 4096 bytes = 50% of each DATA buffer is unusable and thus a
total waste.
Assuming that the BUFNI/BUFND requests for each SHRPOOL are cumulative
BUFNI=7972 and BUFNI=4070 together request 12038 buffers for the INDEX SET,
plus ONE SEQUENCE SET CI and ONE reserved CI for splits, even if the data
set is opened INPUT.
Note that the INDEX is composed of two distinct logical components,1) the
SEQUENCE SET which has exactly one CI for each data component CA, and 2) the
INDEX SET. To the best of my knowledge it is useless to allocate more BUFNI
than the number of buffers required to hold the INDEX SET plus the 2
mentioned above. This is EXPLICITLY affirmed in the documentation for NSR
and nowhere, that I can find, contradicted for LSR. This much BUFNI would
allow a DATA component of a bit more than 2 million 166 thousand cylinders
or 66+ M27 volumes for the two files and still keep the entire INDEX SET for
both files in main storage.
If they are NOT cumulative then the figure drops to about 67 * .66 = 44 or
so M27 volumes.
In either case I'd have to see it (the files) to believe it. Even by today's
standards this is HUGE volume.
Be back at my desk about 10:00 Tuesday
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