It seems like everyone and their brother (and Cameron Lackpour, the younger brother I NEVER had and NEVER wanted) has jumped in on relating the cool things the latest Essbase patch has to offer. So as not to be left out in the cold, I thought I make a few comments as well.
I think this new patch is a real game changer with a lot of cool features. It will have many of us throwing out old optimization techniques and coming up with a whole new set. We will really have to think out side the box to figure out what is best.
That said, There are a few things you might want to consider. First, although this is listed as 11.1.2.3.500, it has significant changes in it. Why Oracle has such significant changes in something that is just a patch, I don’t know, but it certainly better than waiting for a full release of the product. One supposes you could install the patch to get the features like enhanced aggregation for MDX functions and bug fixes, I would test very carefully before using some of the other new functionality without extensive testing.
Next, I would like to go into a little detail on a couple of the new features. In general, the word of caution I would give is to test extensively if you are using any of the new features. While they can give you significant gains in performance, they can cause you some issues.
Fix Parallel
The idea behind fix parallel, is there are many situations where calc parallel goes into serial mode and we as developers know better. We can use Fix parallel to force the calculations into a parallel mode. This implies that we actually know what we are doing and that there will be no conflicts if we go into this mode. During the beta testing, it was determined that Fix Parallel is not as fast as calc parallel in most cases, but is faster than not calculating in parallel mode at all.
Hybrid Mode
We have all been drooling over this idea since it was revealed at Kscope last summer. The poser of a BSO cube with the aggregation speed of an ASO cube. How this is implemented is you take your sparse dimensions and make them dynamic . In addition, you add a parameter to the Essbase.cfg file to urn this feature on. During the beta, TimG tested hundreds of queries against hybrid mode and most performed very well.
This is a huge game changer, or at least it will be. I say that because this initial implementation is limited. There are a lot of things that will cause the cube to revert to BSO mode. Using Dynamic Time series (DTS), cross dimensional operators in formulas, some very common functions in formulas (a list too long to list here), and attribute dimensions forces the cube into BSO mode. Frankly, while I think this feature is fantastic, currently it has a limited use case and until some of limitations are removed, tread lightly. Of course if your cube is doing simple aggregation, then go for it an gain the benefits.
Exalytics – writing blocks back to the same location
As Cameron mentions in his blog post, many though this already occurred, and to a certain extent it does. While blocks are written to a new location, Essbase will look at the free spaces to see if a block can fit into a spot vacated by another block, my guess it seldom happens. Having blocks rewritten to the same location can reduce fragmentation a lot. I’m guessing this is Exalytics only right now because most data in Exalytics is actually in Flash memory or on solid state disk. This is just a guess on my part, but from testing the effect of fragmentation on BSO cubes in the past, I can say heavily calculated cube (like planning) will have vast improvement in speed without having the constant maintenance of defragging the DB.
As I said in the beginning of this post, this release is a real game changer. Oracle development should be commended and applauded for thinking outside the box and leapfrogging to this level of functionality. I can’t wait to see what improvements are on the horizon. See I’m never happy with what I get, I always want more. Gaby Ruben told me at Kscope, his job is to make us all rewrite or optimization presentations every year or two. I think he is keeping his word. We all need to re-examine how we optimize given these fantastic changes to the product.
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