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aggregates

how does aggregates improve query performance.

could u plssss explain me in detail

Thanks in advance

rashmi

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5 Answers

  • Posted on Oct 13, 2006 at 11:16 AM

    Rashmi,

    please check the forum before posting ..

    http://help.sap.com/saphelp_nw04/helpdata/en/7d/eb683cc5e8ca68e10000000a114084/frameset.htm

    Hope it helps..

    Arun

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  • author's profile photo Former Member
    Former Member
    Posted on Oct 13, 2006 at 12:01 PM
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  • author's profile photo Former Member
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    Posted on Oct 13, 2006 at 03:12 PM

    Hi,

    Check the following links

    Business Intelligence Performance Tuning [original link is broken] [original link is broken]

    http://help.sap.com/saphelp_nw04/helpdata/en/06/b5f8926ba22b45bc9eaa589f1c835b/content.htm

    A nice weblog by Vikas Please do check this.on number range buffering,

    /people/vikash.agrawal/blog/2006/04/05/load-lots-of-data-147faster148-with-buffering-number-range

    docs bw loading performance material

    https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/1955ba90-0201-0010-d3aa-8b2a4ef6bbb2

    https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/3a699d90-0201-0010-bc99-d5c0e3a2c87b

    https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/4c0ab590-0201-0010-bd9a-8332d8b4f09c

    and don't miss bw performance knowledge centre, there are e-learning

    Business Intelligence Performance Tuning [original link is broken] [original link is broken]

    A nice weblog by Vikas Please do check this.on number range buffering,

    /people/vikash.agrawal/blog/2006/04/05/load-lots-of-data-147faster148-with-buffering-number-range

    Please reward for the same.

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  • author's profile photo Former Member
    Former Member
    Posted on Oct 13, 2006 at 03:20 PM

    Rashmi;

    As you can see all the links above; in overall aggregates are small cubes inside a cube which holds data from the cube in a pre-calculated (aggregated) form for reports so that when the users execute the report it goes and grab the data from the aggregates instead of going after cube and summrizing all the records...this way it takes less time to popuate those data into the reports.

    Hope this helps.

    BK

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  • author's profile photo Former Member
    Former Member
    Posted on Oct 13, 2006 at 06:16 PM

    In a nutshell, aggregates hold summarized data.

    Let's say you have 10 million records in your Sales InfoCube and your company has 50 salesmen. You want to know the total of sales by salesperson. Without an aggregate, your query has to read 10 million rows from the fact table.

    Since this query runs very often, you decide an aggregate would be a good idea and you create an aggregate at the salesmen level. This aggregate only needs 50 rows to hold the information you need. Now your query only needs to read 50 rows. Why that is faster should be obvious.

    It is important to understand that the user does NOT need to know anything about whether aggregates exist. The BW examines the query and determines if it can answer the query from the aggregate, or whether the query must read the base InfoCube. The BW also takes care of maintaining the aggregates (known as the rollup process) so that when you load data to the InfoCube at night, the BW summarizes the new data and adds it to the aggregates in order to keep them in synch with the base InfoCube. You can also have more than one aggregate, e.g. one to support salesmen reporting, and then another that holds summarized data on products sold to support product sales queries.

    SDN has several papers on how to create aggregates, just give a search.

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