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When I create a new query in BEx Designer, All I define is what all I need from underlined InfoProvider & in what format. I really don’t decide where & in which sequence to look for data during Query execution.   Often I wonder when I execute the query how does OLAP processor look for the data? Which in turn lead to many more wandering questions in mind, to state a few –   1.     Wondered if I execute query first time, it takes longer than second execution immediately. 2.     Will it be faster second time for me or for all the users who execute this query after my first execution? 3.     How does aggregated really help in reducing the execution time? 4.     Wondered that pre-calculation was there only to provide static HTML pages or had some thing to do with performance optimization as well.  Answers of all these questions & more could be understood if I could understand how & in what sequence OLAP processor look for the query relevant data during execution. Understanding it has extreme implications in terms of reaching right tradeoff between “Performance Improvement” & “Resources contributed toward it”  This weblog tries to explain just that –Sequence in which OLAP Processor looks for Query Relevant data–, OLAP Processor –  image 1.     First checks data availability in Local Cache (Which is session dependent, stores in Memory & available in All SAP BW Releases).  2.     If Local Cache is NOT available then will check Global OLAP Cache (OLAP Cache buffers Query result set data in order to improve performance of subsequent query executions. It is session/user independent, stores in memory/files/tables & is available from SAP BW 3.X).   3.      If Global OLAP Cache is NOT available then will look for relevant Aggregates (Aggregates are subsets of fact table data where summary data is stored as part of new, transparent InfoCubes. Aggregates have the same structure as an InfoCube, with transparent database tables surrounded by the dimensions tables).  4.     If No relevant Aggregates are found then it will look into database through InfoProvider.  So In order to improve the performance you need to provide the data to OLAP processor as early in Sequence as Possible  But Doing this has Cost attached to it … Look at the tradeoff & Optimize Query Performance?
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  1. John Skrabak
    I’m always a litle reluctant to criticize someone else’s blogging efforts, but I think this blog entry is just simply repeating SAP’s information ffrom SAP’s OLAP Cache documentation. 

    You need to add some useful application of this information, or perhaps where it’s not always true, etc. 

    (0) 
    1. Vikash Agrawal Post author
      Hi John,
      Thanks a lot for you feedback & more importantly going through this blog.

      I go agree with your comments & would appreciate if you understand reasoning behind it –

      1. This weblog is precursror to another one – detailed one on OLAP Cache – So I thought before going ahead with that one I need to build up.

      2. During my inrecations with many BI consultants ( I have interacted with more than 200 in last 12 months), trust me most of them stumbled upon while explaining this.

      Once again thank you for your comments.

      Regards

      Vikash

      (0) 
      1. John Skrabak
        I’ll be waiting to see the follow on posting. 

        I agree, that the use of OLAP cache is probably not understood by as many, nor as well is it should be, given it’s potential for query performance gains.

        (0) 
      2. Siegfried Lebherz
        Hello Vikas,

        I say thanks for this subject. Sometimes is helpful to find here a documentation – also with feedback of the real world. Further: Items in the sdn are easily to remember – SAP documentation sometimes not.

        Siegfried Lebherz

        (0) 
  2. John Skrabak
    I’m always a litle reluctant to criticize someone else’s blogging efforts, but I think this blog entry is just simply repeating SAP’s information ffrom SAP’s OLAP Cache documentation. 

    You need to add some useful application of this information, or perhaps where it’s not always true, etc. 

    (0) 
    1. Vikash Agrawal Post author
      Hi John,
      Thanks a lot for you feedback & more importantly going through this blog.

      I go agree with your comments & would appreciate if you understand reasoning behind it –

      1. This weblog is precursror to another one – detailed one on OLAP Cache – So I thought before going ahead with that one I need to build up.

      2. During my inrecations with many BI consultants ( I have interacted with more than 200 in last 12 months), trust me most of them stumbled upon while explaining this.

      Once again thank you for your comments.

      Regards

      Vikash

      (0) 
      1. John Skrabak
        I’ll be waiting to see the follow on posting. 

        I agree, that the use of OLAP cache is probably not understood by as many, nor as well is it should be, given it’s potential for query performance gains.

        (0) 
      2. Siegfried Lebherz
        Hello Vikas,

        I say thanks for this subject. Sometimes is helpful to find here a documentation – also with feedback of the real world. Further: Items in the sdn are easily to remember – SAP documentation sometimes not.

        Siegfried Lebherz

        (0) 
  3. John Skrabak
    I’m always a litle reluctant to criticize someone else’s blogging efforts, but I think this blog entry is just simply repeating SAP’s information ffrom SAP’s OLAP Cache documentation. 

    You need to add some useful application of this information, or perhaps where it’s not always true, etc. 

    (0) 
    1. Vikash Agrawal Post author
      Hi John,
      Thanks a lot for you feedback & more importantly going through this blog.

      I go agree with your comments & would appreciate if you understand reasoning behind it –

      1. This weblog is precursror to another one – detailed one on OLAP Cache – So I thought before going ahead with that one I need to build up.

      2. During my inrecations with many BI consultants ( I have interacted with more than 200 in last 12 months), trust me most of them stumbled upon while explaining this.

      Once again thank you for your comments.

      Regards

      Vikash

      (0) 
      1. John Skrabak
        I’ll be waiting to see the follow on posting. 

        I agree, that the use of OLAP cache is probably not understood by as many, nor as well is it should be, given it’s potential for query performance gains.

        (0) 
      2. Siegfried Lebherz
        Hello Vikas,

        I say thanks for this subject. Sometimes is helpful to find here a documentation – also with feedback of the real world. Further: Items in the sdn are easily to remember – SAP documentation sometimes not.

        Siegfried Lebherz

        (0) 
  4. Guido Brune
    Hi,

    thanks for your blog!

    Another interessing this how and when
    OLAP Prozessor does which calculation and operations.

    I had a persentation on OLAP BW3.x
    Technology.

    Maybe someone nearer to
    development could explain difference
    between BW3.x and BW7.x OLAP Procesor
    and processing logic.

    Once again thanks!

    Guido

    (0) 
  5. Guido Brune
    Hi,

    thanks for your blog!

    Another interessing this how and when
    OLAP Prozessor does which calculation and operations.

    I had a persentation on OLAP BW3.x
    Technology.

    Maybe someone nearer to
    development could explain difference
    between BW3.x and BW7.x OLAP Procesor
    and processing logic.

    Once again thanks!

    Guido

    (0) 
  6. Guido Brune
    Hi,

    thanks for your blog!

    Another interessing this how and when
    OLAP Prozessor does which calculation and operations.

    I had a persentation on OLAP BW3.x
    Technology.

    Maybe someone nearer to
    development could explain difference
    between BW3.x and BW7.x OLAP Procesor
    and processing logic.

    Once again thanks!

    Guido

    (0) 
  7. Vasuki Basavanahalli
    Hi Vikas,

    Interesting stuff.I will be looking forward to the main blog on OLAP.

    It would be great if you can address the processing sequences by the OLAP Processor which Guido is refering to(It would be great if that presentation can be shared).

    We have some interesting observations which I can share when we interact the SAP data-source with 3rd party data tools.  

    Good work…
        

    (0) 
  8. Vasuki Basavanahalli
    Hi Vikas,

    Interesting stuff.I will be looking forward to the main blog on OLAP.

    It would be great if you can address the processing sequences by the OLAP Processor which Guido is refering to(It would be great if that presentation can be shared).

    We have some interesting observations which I can share when we interact the SAP data-source with 3rd party data tools.  

    Good work…
        

    (0) 
  9. Vasuki Basavanahalli
    Hi Vikas,

    Interesting stuff.I will be looking forward to the main blog on OLAP.

    It would be great if you can address the processing sequences by the OLAP Processor which Guido is refering to(It would be great if that presentation can be shared).

    We have some interesting observations which I can share when we interact the SAP data-source with 3rd party data tools.  

    Good work…
        

    (0) 
  10. pk kumar
    Hi Vikash,

    Really Thanks for your blog.

    I am new to query ,after go through on your blog Now i am able to undestand the basic concepts of query.

    Brgds
    Kumar

    (0) 
  11. pk kumar
    Hi Vikash,

    Really Thanks for your blog.

    I am new to query ,after go through on your blog Now i am able to undestand the basic concepts of query.

    Brgds
    Kumar

    (0) 
  12. pk kumar
    Hi Vikash,

    Really Thanks for your blog.

    I am new to query ,after go through on your blog Now i am able to undestand the basic concepts of query.

    Brgds
    Kumar

    (0) 

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