One of the constraints you'll see is that IDMS can't write to the LOG
file fast enough. A reduction in overall capacity will adversely affect
IDMS's ability to respond to application calls, whether online or batch,
in a timely manner.
Adams, Tracy wrote:
Okay, this is a continuation of a previous post...
First of all we have an 88 mip cpu that is not constrained in any way.
RMF cpu intervals are 20% during the day and during the 3 hours of batch
100% like a good MVS system can do.
So with the rising cost of software, mainly CICS, we are looking to cut
the mainframe's capacity in half. Now in the simplest math, batch
should double in time and daily rmf stat intervals will increase but
still not hit 100%, as long as no other constraints are revealed.
Some basic tests have revealed results that I can't explain.
Response time in our IDMS transactional system during the day (as record
via PMDC writing smf records translated by MXG).
A typical SAS model of performance for a given online transaction would
be 95% < .5, 4% < 1, 1 % > 1.
When I set a hard cap at 90% the model looks more like 70% < .5, 15% <
1, 10% < 2 and 5% > 2 of that 1% > 3.
When I set the hard cap at 75% the model looks more like 50% < .5, 15 <
1, 20% < 2 and 7% > 2 and 3% > 3.
And when I set the hard cap at 50% the model looks more like 40% < .5,
25 < 1, 25% < 2 and 10% > 2 and 3% > 3. And the users now users are
really complaining now.
RMF type 70 records (cpu) for all four scenerios (100%, 90%, 75% and
50%) show averages in the 20% utilized.
RMF type 74 records (IO) show avg resp in single digits.
UIC hasn't fallen below 255 in 10 years.
Batch... completed in the same time frame set at 25% as it did at 100%.
So if the hard cap sets the amount of Service units consumed not the
actual speed of the processor, why is response time in the online going
so far south when the CPU is still running unconstrained? Why did batch
not slow down?
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Rick
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