--- On Fri, 5/15/09, Frank Swarbrick <fswarbr...@gmail.com> wrote:
------------------------SNIP----------------------------------
> >
> >What does this have to do with anything? Well, the
> typical throughput
> >performance gains seen in the past when going from VSE
> to MVS don't
> >happen because what was giving those (for the most
> part) has already
> >been realized.
>
--------SNIP----------------
OK I will be the first to admit it but I have not seen DOS in 40(?) years.
So if DOS has improved I would be very surprised (as far as I/O improvements).
Did DOS finally as a default support 5 I/O buffers on QSAM? I remember when
SAM-e came out for MVS in the '70's) and it made a HUGE impact on I/O and all
for the good (mind you). My vague memory of DOS was a DTFxx and you had to
specify the 1st and 2nd IOareas and that was needed (IIRC) just to get two
buffers.
In MVS when we added SAM-e we saw a *SIGNIFICANT* improvement in job elapsed
time. Like I said it was 30+ years ago my memory says it decreased run time by
50% to 66% typically and of course some were less and some where more so I do
not want to say average but it was in the area of 50-66 percent. I distinctly
remember getting a call from production support at 0000 something in the
morning says something was wrong as jobs were running way to fast. I assured
them it was a performance enhancement and they would see most jobs running a
lot faster.
Fast forward 5 years in the 80's
Change of job. We brought up MVS and were running VS1 and jobs were running so
fast the operator could not keep up with the manual log he had. Again same call
from production support(different company) as production got done at 630AM
normally on VS1 and on MVS (with SAMe) they were done at 430AM.
The only thing the operators didn't like was that tape drive selection was set
at random so they couldn't premount tapes. In VS1 (IIRC) the lowest tape drive
address was always 380 and the drive was getting beat up on and failing more
often. The CE (customer Engineer) was ecstatic as he wasn't fixing the same
tape drive all the time.
IIRC SAMe was $15 a month charge option then. After a while practically every
flavor of MVS that was being shipped was ordered with SAMe and it became
standard (don't ask me what year).
The bottom line is the MVS had SAMe and I do not recall it ever being offered
in DOS (pick your flavor), are you suggesting that it was, if so how? The DOS I
was used to (granted old) would never have allowed it.
Ed
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