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6 Replies Latest reply: Jan 22, 2013 5:53 AM by name_and_address_withheld RSS

Calc Cache

name_and_address_withheld Journeyer
Currently Being Moderated
I read that the max you can set the CALCCACHEHIGH is 200,000,000 bytes. I want to set it to the max, I assume this means that when we run a calc with Set cache high, it will only use this amount of memory if it needs to and not take it irrespective?

Are there any "gotchas" in setting the limit this high? I can test this setting, but I am worried about prod.
  • 1. Re: Calc Cache
    sunil k Journeyer
    Currently Being Moderated
    We have it set at the same value (200,000,000) in our prod environment and there are no issues. ESSBASE is on solaris. As long as you have enough memory available, it should be good.

    Regards,
    Sunil
  • 2. Re: Calc Cache
    CL Oracle ACE Director
    Currently Being Moderated
    I think every calculation that you run will take that 200 megabytes. So one calc = 200 MB, two calcs run simultaneously = 400 MB, etc., etc., etc. Just something to be aware of in a budgeting (like Planning) environment.

    Just be aware that you need that amount of real RAM, otherwise you'll end up paging memory to disk.

    FWIW, I try to always use as much calc cache as possible -- servers are big, memory is cheap, and hopefully none of the boxes I am running on are maxed out. It can help, some, with the calc time so I use it till I can't.

    Regards,

    Cameron Lackpour
  • 3. Re: Calc Cache
    TimG Guru
    Currently Being Moderated
    I think you're right Cameron, and it's one calc cache per thread too, so be careful with high cache settings and CALCPARALLEL. Rick Sawa's post here has an excellent in-depth discussion: http://oracleinfogram.blogspot.com/2009/02/hyperion-essbase-optimization-what-is.html
  • 4. Re: Calc Cache
    name_and_address_withheld Journeyer
    Currently Being Moderated
    TimG wrote:
    I think you're right Cameron, and it's one calc cache per thread too, so be careful with high cache settings and CALCPARALLEL. Rick Sawa's post here has an excellent in-depth discussion: http://oracleinfogram.blogspot.com/2009/02/hyperion-essbase-optimization-what-is.html
    ok, this is something I was afraid of. I cannot assume that calcparallel will not be upped to get a (in my opinion) cheap boost in calc performance, temporarily or permanently - and therefore putting the server at risk. We have a bunch of memory, but we also have a lot of calcs running every hour, and I am sure that the memory usage will quickly spiral in a "perfect storm" event.

    Of course it would be nice to be able to be a little more granular with the calc cache setting in a calc script outside of the high/default/low settings, i.e. setting a value independent of the config file.....pipe dream probably.
  • 5. Re: Calc Cache
    TimG Guru
    Currently Being Moderated
    Also, very interesting comment Rick makes (admittedly, now almost four years old) in that article:
    It is important to know that searching through the bitmap is not indexed and results in the strong suggestion NOT to allocate more than 50 MB of RAM to the CALC CACHE, because the effectiveness of the CALC CACHE search algorithm tails off beyond 50MB. When Essbase is unable to achieve multiple bitmaps with a single anchor using 50 MB or less, break the so-called “hourglass” motif and move non-aggregating sparse dimensions below the last and largest sparse (anchor) dimension. The objective is to reserve memory for Essbase to be able to place as many aggregating dimensions as possible into the bitmap.
    Whether Rick's statement re 50MB still holds or not, I think you should be testing the CALC CACHE values to see where you actually get benefits (and then set no larger) - and thinking about it, you may see 'step' changes as different bitmap / anchor configuration are applied.

    Clearly the interaction between CALCPARALLEL, CALC CACHE and outline order is complex (more complex than can be captured in a simple rule-of-thumb!).
  • 6. Re: Calc Cache
    name_and_address_withheld Journeyer
    Currently Being Moderated
    Yes I saw that part too. I was going to test it out and see what happens if I went north of 50mb...I mean not every cube is the same as we probably all know too well.

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