IBM for many years supplied a macro or subroutine called TRKCALC that can be
used for space calculations. I don't know if it's still around. GIYF.
The actual formula used is:
Physical records per track = 1729/(10+K+D)
D= 9 + (DATALEN + (6x((DATALEN+6/232)) +6/) /34
K = 0 if non-keyed
K= 9 + (keylen + ( 6* ((keylen+6/232)) + 6) /34 (if keyed)
1) I would imagine it can , but I am baffled as to where it would be specified.
The most likely options are in the CDS, or IGDSMSxx.
2) See # 3.
3) SLED devices generated the recommendation for 1/2 track blocking for the
following reasons:
a) Maximizing the use of space.
b) Minimizing physical IO to the device .
With the advent of RAID devices, the physical IO portion has much less
importance. There might be some performance IOS related overhead due to
increase number of IO requests
With the reduction in DASD prices, does the percentage of utilization matter as
much as it used to
I have not heard of any research in this area? Is Pat Artis still active, or
has he retired?
HTH,
<snip>
I have gone through a few manuals and cannot determine the answer to the
following questions. Any guidance is appreciated
1) Can the SDB be adjusted from half-track to another setting (quarter or
full)?
2) Are there any new best practices for SDB that have changed in the last 20
years?
3) Is Half-track still considered OPTIMUM?
Since the storage arrays are so fast, I would think that maybe full track would
not be that much of a performance impact any more.
I have been working offlist with a couple of people with JCL and BLKSIZE and
SPACE Sizing. I am trying to figure out how to make the formula more accurate.
When I calculate space - I use full trace blocking. However, I find when SDB
uses half-track, my math is off.
</snip>
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