It has been too long since I last updated my blog, not because of a lack of desire, nor even a lack of anything to say – I have just been too busy!
A large part of that busyness has been associated with upgrading the iT-Workplace Mdx query capability to support SAP Business Warehouse. I have to admit that when I first started this project I was sceptical about BW as an Olap data source. I had heard quite a bit of negative response to the performance and architecture of BW therefore started the work with a fairly low expectation. Having worked with it for a while both in test and production environments I am now more positive.
SAP have certainly taken an unusual approach to implementing Olap for people who come from a Microsoft background. The SAP tools allow you to build queries that effectively define a sub-cube for analysis. This allows the performance of the implementation to be managed by limiting the amount of data a user will navigate at a given point in time. The downside is in the flexibility to investigate data which exists in the cube but is outside of the query definition. Given this restriction the performance of the resulting "views" is quite adequate for typical Olap navigation without being stellar.
The queries bring on their own complications when using Mdx due to some SAP specific extensions that allow you to define the "variables" that limit the scope of the query. SAP’s core Mdx implementation is also very basic when compared to Analysis Services but then this is also true of TM1.
From the exposure I have had so far I would say the biggest problem with SAP BW is actually in the warehouse administrators unerstanding of what makes a usable cube/query. Most of the data I have worked could have been improved greatly if some usability testing had been done with end users. This is not of course a problem that is unique to SAP, I have seen some apalling Analysis Services implementations in my time, but because the SAP world is quite closed there does seem to be a lag in design skill for BW implementations.
I would love to implement the warehouse experiment into BW some time to see how easy it would be to create a rich Olap experience for end users. Somehow I suspect that I won;t have time to do this in the near future……..
Do you know where I can find more sites with SAP Bw practice questions and answers. I found one with 80. Is that how many are on the test?SAP BW Practice Test Qustions and answershttp://www.hometutorials.com/SAP-BW/
I was wondering if you have stumbled into issues with BW cube/query being accessed via XMLA. Specifically, are there any cube/query special configurations or things to avoid problems with XMLA access?Enrique
EnriqueThere are 2 significant issues that I have encountered. First (unless you really want to write a soap client) you need some kind of Adomd style provider to work with SAP. We are using Adomd.NET but not the standard provider shipped by Microsoft. Microsoft developed a separate provider that is shipped with Reporting Services that has extensions to cope with diferences in SAP syntax. Unfortunately thsi provider is not available for free distribution – we have had to engage in a royalty agreement to ship it.Second, your client needs to understand SAP BW MDX extensions such as the "SAP VARIABLES" clause. This is neccesary if you intend to work with SAP Queries. There are also a few issues in retriving freindly names for things like queries and infocubes.There are some minor restrictions such as not being able to put 2 hierarchies from the same dimension into a query at the same time but otherwise the SAP provider works pretty much as you would expect.