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luban
New User
Joined: 19 Nov 2005 Posts: 26 Location: Shanghai, China
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Hi,
I have an question about job running time. Is there anyone could give me any advise? Thanks.
I ran a job twice in one day, but 1st time it just cost 6 mins, 2nd time it cost almost 44 mins.
I've checked JESYSMSG of the job and found the step which cost the time difference.
I found the difference only is STEP SERVICE:
STEP SERVICE 15,043,989
IEF373I STEP/PS010 /START 2008214.0841
IEF374I STEP/PS010 /STOP 2008214.0846 CPU 1MIN 09.23SEC SRB 0MIN 00.48
STEP SERVICE 16,251,120
IEF373I STEP/PS010 /START 2008214.1414
IEF374I STEP/PS010 /STOP 2008214.1458 CPU 1MIN 15.51SEC SRB 0MIN 00.56
So is there anyone could give any advice about " STEP SERVICE " or any other aspect I missed?
Thank you very much. " ) |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006 Posts: 19244 Location: Inside the Matrix
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Hello,
You have observed a difference in elapsed time. Elapsed time is not typically used to measure the cost of a job.
The difference in elapsed time is most likely due to the difference in what else was running on the system or why the second job had to wait for something (like a tape mount).
If you notice the other statistics presented (step service, cpu, srb) they are quite close. These more correctly point to the "cost" of the job.
It is common to see very different run times caused by other activity in the system. |
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luban
New User
Joined: 19 Nov 2005 Posts: 26 Location: Shanghai, China
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Hi dick scherrer,
Following is the other statistics, actually most of them are really close, except STEP SERVICE.
Do you have any idea about this?
(Actually here's no contention message in the log, so I'm really confused ) |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006 Posts: 19244 Location: Inside the Matrix
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Hello,
Quote: |
Actually here's no contention message in the log, so I'm really confused |
No, there typically will not be. . . The system is set to "take turns" between processes that are competing for resources. It does this automatically. What happens is that the more things that are running, the slower some things will run. Part of this is due to volume and part of this is due to system priorities.
From what you've posted, things appear to be quite normal. The runs are very similar - the second job using slightly more resources that the first. For a deeper carification you would need to talk with your performance measurement people.
As i mentioned earlier, elapsed time is not as predectable. Many things can influence run-time/wall-time. |
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luban
New User
Joined: 19 Nov 2005 Posts: 26 Location: Shanghai, China
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Hi d.sch,
Thank you very much for your advice.
Actually I will talk with my SME tonight.
It's really weird that just slightly difference can cause 44 mins delay...
Anyway, thank you very much |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006 Posts: 19244 Location: Inside the Matrix
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Hello,
Quote: |
It's really weird that just slightly difference can cause 44 mins delay... |
The slight difference is not causing the difference in run times.
The load on the system at different times is most likely causing the difference in run-time.
If your system has very little going on over the weekend you might try to run the job a few times (with all of the exact same data) and see the run-times and other resource usage. |
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006 Posts: 6250 Location: Mumbai, India
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Quote: |
It's really weird that just slightly difference can cause 44 mins delay... |
You might try by requesting Performance Monitoring Team to set up strobes in your JOB.. |
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luban
New User
Joined: 19 Nov 2005 Posts: 26 Location: Shanghai, China
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Hi Anuj D,
Strobes?
Could you give me more explanation about this?
Thank you very much. |
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expat
Global Moderator
Joined: 14 Mar 2007 Posts: 8797 Location: Welsh Wales
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Not too much difference in the service units or CPU times used, could well be external influences.
Is this a cloned run using EXACTLY the same input data or with different input data in the second job run ? |
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luban
New User
Joined: 19 Nov 2005 Posts: 26 Location: Shanghai, China
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Hi expat,
Yes, it's EXACTLY the same input data in the second job run.
Thanks. |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006 Posts: 19244 Location: Inside the Matrix
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Hello,
You are spinning your wheels . . .
You cannot "tune" elapsed time. You can (sometimes) improve elapsed time by tuning actual resource consumption when one task uses more resources than another.
Your 2 tasks use basically the same amount resourses. The way to get the same elapsed time for multiple runs is to control the mix of processes that are running on the computer to always be the same when this process runs.
As i mentoned earlier, plan on running the same process multiple times over a weekend or some other time when system use is very low. |
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Terry Heinze
JCL Moderator
Joined: 14 Jul 2008 Posts: 1249 Location: Richfield, MN, USA
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dick scherrer wrote: |
...You cannot "tune" elapsed time... |
You can stop all initiators except the one you use. Just kidding; please don't try this at home. |
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expat
Global Moderator
Joined: 14 Mar 2007 Posts: 8797 Location: Welsh Wales
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Quote: |
Just kidding; please don't try this at home. |
Much more fun trying at work instead ....................... |
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006 Posts: 6250 Location: Mumbai, India
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006 Posts: 19244 Location: Inside the Matrix
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Hello,
Using Strobe to "watch" your job will most likely just waste your time. Strobe could point out bottle-necks in your process, but they would most likely be consistent rather than what you have seen.
One more time. . . The reason you see different elapsed times is most likely due to other activity going on in the machine. Your code used nearly the same amount of resource. If the resource used varied by some large amount, that might account for the difference in elapsed time.
The resource usage from both runs was quiite similar, so the difference in run time is probably not due to the actual process.
One thing to look at might be if this process uses some shared vsam or database data. If other processes heavily hit either, there will be an impact on the process you are interested in. |
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006 Posts: 6250 Location: Mumbai, India
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Hi Dick,
Perhaps I got the context of the thread little different, per you, please let me know when strobe should be set-up for a JOB? |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006 Posts: 19244 Location: Inside the Matrix
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Hi Anuj,
Strobe is quite good at helping to identify bottlenecks.
If a process consistently preforms poorly, Strobe might be used to isolate where various concentrations of cpu or i/o is being used.
The job for this topic does not seem to fall in this category. With the same input, it runs for different lengths of wall-time. It does not use (from what we've seen) different amounts of resources. Which leads me to believe the difference in elapsed/wall tme is due to external influences rather than something in the code of "this" process. |
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