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Cube Compression & Process Chains

Hello Friends

Few Questions as I am a beginner.

1) What is the entire concept behind Cube Compression. Why is it preferred for Delta uploads and not for full uploads.

2) What do we mean by deleting and creating indexes using process chains.

3) What is meant by the process chain "DB Statistics Refresh"? why do we need it.

Any help is appreciated. Points will be generously assigned.

Thanks and Regards

Rishi

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    author's profile photo Former Member
    Former Member
    Posted on Jan 30, 2008 at 06:21 PM

    Hello Rishi,

    As you may know, an InfoCube consists of fact tables and dimension tables. The fact table hold all key figures and the corresponding dimension keys, the dimension tables refer from dimension keys to InfoObject values.

    Now, there is not only one fact table but two - the F table and the E table. The difference from a technical point of view is just one InfoObject: 0REQID, the request number. This InfoObject is missing in the E table. As a result, different records in the F table could be aggregated to one record in the E table if they have the same key and were loaded by different requests.

    As you may know, you can delete any request from an InfoCube by selecting the request number. And here is the disadvantage of the E table. As there is no request number you cannot delete a request from this table.

    When data is loaded into an InfoCube it is stored in the F table. By compressing the InfoCube records are transmitted into the E table. Because of the disadvantage of the E table it can be defined per InfoCube if and when data has to be transmitted.

    More information can be found here: http://help.sap.com/saphelp_nw70/helpdata/en/ca/aa6437e7a4080ee10000009b38f842/frameset.htm

    An index is a database mechanism to accelerate the access to single records within a table. In BW indexes are used to increase the reporting speed.

    Whenever data in a table is added or deleted - in our case loaded - the index has to be modified. Depending on the amount of changes in the table it could be less time consumpting to delete the index, load without an existing index and to rebuild the index afterwards. This can be done in process chains.

    DB Statistics is something special for an Oracle database. As far as I know (I do not work with Oracle) it is used to optimize SQL commands which are needed for BW reports.

    I hope that these explanations are helpful.

    Kind regards,

    Stefan

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  • Posted on Jan 30, 2008 at 06:25 PM

    Just to add to stefan's reply, using DB statistics enables the system to optimise the database access plan..and thus increases performance...

    usually we use 10-20 percent of data for DB statistics,,,

    Hope it helps,

    Ajay

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  • author's profile photo Former Member
    Former Member
    Posted on Feb 01, 2008 at 03:24 AM

    Check this doc abt performance tuning for detailed insights

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

    Hope it Helps

    Chetan

    @CP..

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