We're looking at activating MT. We're curious how wide spread the use of MT is.
I have been using multitasking on our back-end CVs for 10? Years – the increase cpu was negligible, and the improvement in throughput was noticeable.
When run depth = 3, subtasks = 6m and ziip = y
At our peak, we were running 500 million tasks / week – a bit less now – but still great
The only problem we ever head – on front end cvs – we had issues when multitasking tasks were wt8ingi9ng to the internal reader – got cv-ending abends – but there is an optional bit that my correct that now
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Mark, I used MT with good success at my previous employer and have implemented it at two client sites as a consultant. You might want to start small and increase the count based on observations.
We run an MT level of 4 on a box with 3 GPs.
Charles (Chuck) Hardee<mailto:Chuck.Hardee@ThermoFisher.com>
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Hi Mark, before activation of MT, check the effectiveness of MVS cpu allocated by z/OS to your IDMS region. It is useless or even painful to allocate extra TCB's to your IDMS region if z/OS doesn't allocate now enough CPU to your IDMS region. MT uses MPMODE locking which consumes extra CPU.After MT activation, watch your TCB's usage with DCMT DIS MPMODE and DCMT DIS SUBTASK EFFECTIVENESS .
In support of Philippe’s comments…..
In a really enjoyable past life, to meet “Six Sigma” belt requirements, we did “tuning” projects. This for all of GE’s DBDC environments, CICS, DB2, IDMS & etc, and their associated products.
This was a “speed and profitability” analysis. AKA “do it faster and lower CPU”.
We examined and analyzed every IDMS user setting, including the famed “Bob Dobbs zaps”, with actual production work loads.
The result for IDMS multitasking and I quote “Recommendation: Turn off multitasking. Unless the region is , It is unlikely that the region requires multiple TCBs to get the requested work done. The IDMS multitasking option can cause the region to consume 20% more CPU to manage the additional TCBs.”
No region at GE benefited from multitasking.
When I arrived here multitasking was turned on. I exercised the sigma project here. End result was multitasking was turned off, while implementing other “speed and profitability” recommendations. The average reductions were 37% CPU and 20% response.
I sure do miss my former GE “CDAC” peers, Ron Lamb, Dan Hall, Brian Schroeder, Doug Jolley, Jack Koebbe, George Cable, Gerry Irwin and Dave Burton.
Some IDMS sites would get minor advantages of MT. I am thinking about site using IDMS only as a DataBase server with DB requests coming only from CICS and Batch programs. MPMODE DB will be the most used in this configuration as almost none user code is running inside the CV and MPMODE locking will restrict the usage of only 1 TCB.
On a site using IDMS/DB/DC with user code running inside the CV, the several MPMODEs will be dispatched into the multiple TCB's assigned to IDMS.
In every situation, deployment of MT must be monitored on a regular basis.
Interesting comments Rob. I wonder if John Siraco would like to add anything.
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