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IBM LPM performance issue

Posted on 2014-02-13
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I recently had performance issues when I was LPM'ing a DB server from one frame to another, The server had 56GB and took almost an hour, But I have a similar machine with the same metrics and had 10% more load than the previous one which took only 40 min.

Also on the first one which I was LPM'd had application slowness and queries hanging, So does LPM have performance issues because IBM says its not the case...
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Question by:aanya247
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woolmilkporc earned 500 total points
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If the whole system (not just the LPAR) in question runs near 100% (all CPUs) I can imagine that the small LPM overhead could have an effect on LPAR peformance, but if there's a bit CPU left no one should even notice that LPM is running (but see below).

If you don't have a dedicated connection LPM slowness could be due to network congestion, but from my experience the greatest impact on LPM speed is always by memory activity.

It's not the consumed amount of main memory which counts, it's the change rate.

A big amount of static memory can be transferred just easily, but continuously changing memory content is a challenge for LPM.

The more "dynamic" the memory is the longer LPM will have to try to transfer as much memory as possible, and the longer the whole process will take.

There is a short moment where LPAR processing has to be suspended in order to transfer the remaining memory content (which is too dynamic to be transferred on the fly) and to pass control to the target system.
The higher this amount of memory the longer the suspend time - this can potentially lead to application outages.

wmp
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by:aanya247
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thank you so much for the explanation, So u know how long is the theoretical suspend time according to IBM , Or Is this not published....
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by:woolmilkporc
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This is not published, as far as I know.
 
Certainly because it depends on too many things, but certainly also because IBM don't want to upset the apple cart (or want to let sleeping dogs lie, if you prefer).
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by:aanya247
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Thank you...
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