Ideal Time Slice for AS400

[Mario Manfredi]

Hi

Set the ideal time slice [20ms-2000ms] for AS400 in very difficult, because
this machine is unforeseeable.
A subsystem with 1000 quiet jobs and 1 mad job cause a slowing down
incredible.

Do you have any ideas ?

Yours sincerely, Dr. Mario Manfredi

email: mar...@mbox.vol.it

[Paul B. Davidson]

I do quite a lot of performance management and tuning for a number of clients, and what I and my colleagues have discovered is that, in general, Time Slice makes only a small amount of difference in the grand scheme of things.  Time Slice merely controls the maximum amount of time a particular job *can* remain active in the CPU before it definitely gets told to wait (if there is something else waiting to use the CPU- if not, the wait is almost non-existant).

 

While I have no clear grasp of the problem you are describing, and have no way to say what the actual solution might be, you may consider looking at priority and memory allocation before looking at the time slice parameter.  If there are 1000 priority 50 jobs, and 1 priority 49 job, that one job will get the lion's share of the resources.  If all 1000 jobs are taking as little as 100K of memory, and all are attempting to be active, your AS/400 would (theoretically) need 100 Megabytes of memory in that subsystem's memory pool to prevent paging overhead from eating your response time, irrespective of the one job that seemingly is taking all the resources.

 

If you could paint a clearer picture of the actual circumstances, including priority, AS/400 model, type of jobs, etc, perhaps I could answer the question a little better.

 

Good luck!

-Paul B. Davidson