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Infocube Indexing

Former Member
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Hi Guys,

I was going through some stuff to improve the performance for our Queries.Could anybody please give in details about the indexing mechanism for infocubes.Can we change the index type from Bit map to B-tree in fact table.How can I get the details about indexes which are already created in system like index type, whether primary or secondary and also can I look at the index structure where system stores it?

Thanks for your help.

Rgds

Amit

Edited by: AJ0099 on Nov 6, 2009 4:31 AM

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Answers (1)

Answers (1)

former_member181964
Active Contributor
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Former Member
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Hi Surendra,

Pretty good Links, but to my surprise none of them discuss anything about indexes.

Rgds

Amit

Pravender
Active Contributor
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Hi

Check these two links

[http://www.sdn.sap.com/irj/scn/weblogs;jsessionid=(J2EE3417200)ID1179901350DB11213920781603911361End?blog=/pub/wlg/14359]

[http://www.sdn.sap.com/irj/scn/index?rid=/library/uuid/e0b28d18-f383-2c10-a780-a52349715b54&overridelayout=true]

Hope it helps!!

Former Member
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Hi,

you can delete the indexes and agian we can create the indexes also . you want more detail about primary index , secondary indexes , go to db02 there you can find in which are all infocube is not maintained in secondary indexes and primary indexes.

Regards

sivaraju

Former Member
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Hi Guys,

It still no where tells me how to convert bit map to b-tree or vice versa.

rgds

amit

Former Member
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Hi

The advantages of using bitmap indexes are greatest for low cardinality columns: that is, columns in which the number of distinct values is small compared to the number of rows in the table. If the number of distinct values of a column is less than 1% of the number of rows in the table, or if the values in a column are repeated more than 100 times, then the column is a candidate for a bitmap index. Even columns with a lower number of repetitions and thus higher cardinality can be candidates if they tend to be involved in complex conditions in the WHERE clauses of queries.

For example, on a table with 1 million rows, a column with 10,000 distinct values is a candidate for a bitmap index. A bitmap index on this column can out-perform a B-tree index, particularly when this column is often queried in conjunction with other columns.

B-tree indexes are most effective for high-cardinality data: that is, data with many possible values, such as CUSTOMER_NAME or PHONE_NUMBER. In some situations, a B-tree index can be larger than the indexed data. Used appropriately, bitmap indexes can be significantly smaller than a corresponding B-tree index.

In ad hoc queries and similar situations, bitmap indexes can dramatically improve query performance. AND and OR conditions in the WHERE clause of a query can be quickly resolved by performing the corresponding Boolean operations directly on the bitmaps before converting the resulting bitmap to rowids. If the resulting number of rows is small, the query can be answered very quickly without resorting to a full table scan of the table.

go through this link

http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96524/c11schem.htm#5381

BI query checks the available resources in the following order;

1) OLAP cache

2) BI Accelerator indexes

3) Cube aggregates

4) Cube indexes

As long as the BIA indexes are green for this cube, having the cube indexes deleted won't impact the user experience

Santosh

Former Member
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Hi Santhosh,

Your link is helpful and I have provided the points for that too..but my question still stands How can I change the index type from Bit map to B-tree for an infocube fact table.

Rgds

Amit

Edited by: AJ0099 on Nov 7, 2009 5:56 PM

Former Member
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Hi.

as far as i know,if you check your dimension with "Line Item Dimension",then SAP BW automatically transfer from bitmap index to B-tree index.

Best Regards

Martin Xie

Former Member
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Hi Martin,

But for that I can only do it when I have only one characteristic in the Dimension.I am looking at some other way to make index type on my choice( Bit map or B- tree).Is there any transaction code where I can see what type of index is it on any specific table or column?

Rgds

Amit

former_member181964
Active Contributor
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Hi,

Please check the Blog on Indexing, I hope which will help you about Indexing..

/people/debanshu.mukherjee2/blog/2009/05/22/sap-bw-indexing-scheme-oracle

See this PDF, it is having the details of Bitmap and B-tree indexing.

http://www.erada.com/articles/InfoCube_Modeling_Dimension_Design_Erada_BWInfoAlert.pdf

http://www.oracle.com/technology/pub/articles/sharma_indexes.html

Thanks

Reddy