Question

How can I make my OLAP exectute faster?

Asked by: gosi75

I'm having big difficulties with an existing OLAP where the end user uses Excel to pivot the data. The OLAP has 6 dimensions where 5 of the dimension have from 34 to 2266 rows and the last dimension, has around 275.000 rows. The fact table has about 165.000 rows and around 2.500 rows are added each month.

The OLAP has few calculated members, some YTD and MAT calculations. Those measures are the most important for the client, along with attributes from most of the dimensions. When attributes from the biggest dimension, the one with 275.000 rows are added to pivot table, it can take up to few hours to execute.

I just recently heard about the non_empty_behavior function and added that to the members, and a query that before took around 3-5 hours took only few seconds. Later, I found out that there are a lot of data missing. There are few things I think is a bit odd about this, and that is probably because I don't fully understand the behaviour of the non_empty_behavior, but when I do add the non_empty to my calculated member in SSAS f.exs. [MAT - Number Of Packages], I get the correct sum value for, but in the detail view it's missing. In the attached files(September_incorrect.pdf), there is 2.060 in grand total but the detail view only show the one for september, 496 units.
How come the grand total is showing when the detail data are missing?

What are my alternatives here, is there any other function I could add to my calculated measures in SSAS in order to speed up the exectution time without missing any data?

SELECT {
		[Measures].[Number Of Packages Sold],
		[Measures].[MAT - Number Of Packages Sold],
		[Measures].[Year to date - Number Of Packages Sold]} DIMENSION PROPERTIES PARENT_UNIQUE_NAME ON COLUMNS , 
NON EMPTY CrossJoin(
					Hierarchize({DrilldownLevel({[Product].[Product Information - By Name].[All]})}), 
					Hierarchize({DrilldownLevel({[Product].[Strength - number].[All]})})) DIMENSION PROPERTIES PARENT_UNIQUE_NAME ON ROWS 
FROM (
		SELECT ({[Product].[Product Information - By Name].&[Product A - 141945 - 0,18 - mg - 100 - stk], 
				 [Product].[Product Information - By Name].&[Product B - 141945 - 0,17999999 - mg - 100 - stk]}) ON COLUMNS  
		FROM [MDIA])
WHERE ([Dates].[Date hierarchy].[Year].&[2009].&[3. quarter].&[2009 - September]) CELL PROPERTIES VALUE, FORMAT_STRING, LANGUAGE, BACK_COLOR, FORE_COLOR, FONT_FLAGS
 
 
--This is example of one of my calculated member from SSAS 
CREATE MEMBER CURRENTCUBE.[Measures].[MAT - Number Of Packages Sold]
 AS AGGREGATE(LastPeriods(12,[Dates].[Date hierarchy].currentmember),[Measures].[Number Of Packages Sold]), 
/*NON_EMPTY_BEHAVIOR = { [Number Of Packages Sold]}, */
VISIBLE = 1  ;

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september-incorrect.pdf
- 13 KB
september-incorrect.pdf

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Asked On: 2009-10-15 at 07:44:08ID24815014
Tags: OLAP
,; MDX
,; EXCEL 2007
,; SSAS 2008
Topics: OLAP
,; SQL Server 2008
Participating Experts: 2
Points: 500
Comments: 11

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Answers

by: agandauPosted on 2009-10-15 at 13:35:17ID: 25584613

Just to be clear, what do you expect the result set to look like? Should the 496's be 2060's?

Also, are any of these dimensions parent/child?

I'm trying to recreate the issue on my end.

by: gosi75Posted on 2009-10-15 at 16:07:41ID: 25585754

There should be 2 rows in the result set, one with 496 and other one should have 1.564( the total for the last 11 month), total of 2060.
But the 1.564 is missing as I did add non_empty_behavior to the [MAT - number of packages sold] calculated member, but still I´m able to see the total of 2.060, which is the correct amount for the MAT - Number of packages sold in that month, I think that is a bit odd but on the other hand I don't fully understand the behavior of the non_empty_behavior.

And, none of these dimension are parent/child.

by: srnarPosted on 2009-10-16 at 04:36:50ID: 25588507

Non_empty_behavior is usually easy to understand. When the basic measure is empty the calculated is empty also. Also note that there can be more than one basic measure quoted.

I have sometimes problem with the aggregate function which is used in your case. Try to replace with SUM function.

by: gosi75Posted on 2009-10-16 at 06:18:24ID: 25589185

I tried to replace it with the SUM function but that did not make any difference.

About the date hierarchy agandau you posted in my other post, I think that could be something wrong with how the date is set up, I enclose a screenshot of my Attritute relationship for the date dimension from SSAS. Do you spot any serious fault how it's set up?

Attribute-relationship.png
- 47 KB
Attriube - relationship from SSAS

by: agandauPosted on 2009-10-19 at 13:51:56ID: 25608907

Yes, I'd change that so that the quarters and years are *not* directly related to the date, but instead are related through the hierarchical structure.

I'm not familiar with how all that looks in 2008 -- a bit different than what I'm used to.

Attached is how I suspect it would look when set up properly. When the attribute relationships are good, then the aggregations will be more fully taken advantage of, because the design will then "know" that all the months add up reliably to quarters and quarters to years, etc.

gosi-date.bmp
- 1.1 MB
Proposed date attributes

by: agandauPosted on 2009-10-19 at 14:48:42ID: 25609347

Also, read this:

http://sqlblog.com/blogs/mosha/archive/2006/10/25/time-calculations-in-udm-parallel-period.aspx

Not all of it is entirely relevant to your specific question, but all of it certainly is worthwhile reading and learning. It may trigger some design considerations for your date dimension and your measures.

Hope this helps.

by: gosi75Posted on 2009-10-19 at 15:49:21ID: 25609657

I can't actually change all of the the attribute relationships, I can make Day --> Month Name - Year --> Quarter but when I try to connect Quarter to Year I get this error:
"The member count of the related attribute, 'Year', is greater than the member count of the source attribute, 'Quarter'.

You also wrote in the jpg you attached, that you presume that each of these attributes are 'fully qualified' date members. I think some of them are not, but I'm not quite sure which of them are not fully qualified. I attach a pdf with the date members, would be great if you could look at it and let me know which of them you would consider not fully qualified date members.

date-members.pdf
- 70 KB
date-members

by: agandauPosted on 2009-10-19 at 21:25:24ID: 25611058

Your "year" and your "month name year" are more like what you're looking for.

What I mean by fully qualified is that the actual values that become the members of the lower levels of the hierarchy belong to one and only one of the members higher up.

I.e. rather than having quarters Q1, Q2, Q3, Q4, they have to be Q1 2009, or Q1 2008. Each of these belongs to one and only one year, while something called simply "Q1" belongs to every year.

So this way you end up with more quarters than you have years, which is what the designer was barking about with the terse error message. It wants a tree, and you want to give it a tree, but the members need to be unique.

I've attached an excel spreadsheet (no macros within) that can help you generate a date dimension. It's tailored for use within analysis services. One tab has a create table sql statement, and the other has rows in it that contain my preferred dimension table design. The last column reads all the values in the table and generates sql INSERT statements so it's pretty easy to "cook" into SQL.

AttributeRelationships.jpg
- 74 KB
Diagram of attribute relationships based on contents of spreadsheet.
DateDimension.xlsx
- 75 KB
Date dimension values

by: gosi75Posted on 2009-10-22 at 05:19:32ID: 25633194

I've been fighting to get this to work as you suggested, I've now altered the attribute so that they would be considered as a fully quilafied members. When I deploy the OLAP, I get this error:
"The member '&[3. quarter]' was not found in the cube when the string, [Dates].[Date hierarchy].[Year].&[2009].&[3. quarter].&[2009 - September], was parsed."

I've changed the Named Calculation in the Data Source View so that instead of 1.quarter, 2.quarter for Quarter named calculation, I get Q1 'year', Q2 'year', etc.
Do I need to alter it somewhere else, I have looked and looked and I just don't understand why it's still trying to parse [Dates].[Date hierarchy].[Year].&[2009].&[3. quarter].&[2009 - September] ?

by: agandauPosted on 2009-10-22 at 13:29:27ID: 25638634

in the dimension designer, when you have one of the attributes selected look at its properties. Are you sure they're pulling from the columns in the DSV that you think they are?

Obviously you won't match the names I have in my picture necessarily, I'm just including the pic so there's no confusion about one of the places you need to check.

dimension-key-and-name.PNG
- 12 KB
Properties of attribute show where name and key come from in dsv

by: gosi75Posted on 2009-10-27 at 08:39:53ID: 31641657

I got this finally to work and it's amazing how fast it's running now. Thanks for the big help and your patience. Thanks again, cheers
gosi

20120131-EE-VQP-002

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How can I make my OLAP exectute faster?

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OLAP

MDX

EXCEL 2007

SSAS 2008

OLAP

SQL Server 2008

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