Why BSO Disk Space doesn’t follow Block Density

When choosing which BSO (or Hybrid) dimensions to make dense and which to make sparse, a higher block density is generally considered ‘better’. This is a simplification, as the densest combination isn’t always the best performing, but bear with me. The point I want to make and explain in this post is this:
When using bitmap compression, squeezing a given set of data into a denser arrangement doesn’t always result in a space saving of the same magnitude
This isn’t totally intuitive, and it can come as surprise to see that your huge increase in block density has only made a modest dent in the size of your .pag files.

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Automatic CALCTASKDIMS and Empty Tasks

Some Old News

One relatively unsung enhancement to Essbase in was a change to CALCTASKDIMS behavior.  Before, CALCTASKDIMS defaulted to a value of 1.  From,  Essbase selects a value for CALCTASKDIMS automatically unless overridden by the user with either the CALCTASKDIMS .cfg file setting or the SET CALCTASKDIMS calculation command.

So why am I blogging about this years after came out?  First, there is a good theoretical reason why the above Essbase ‘enhancement’ might have a seriously negative effect on calculation performance, which can be especially surprising when it occurs following a supposed upgrade.  Second, this actually bit a coworker a few days ago, and it’s always satisfying (for me, if not my coworker) when empirical data and theory coincide.
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