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Link to Content's target Space :

https://wiki.sdn.sap.com/wiki/display/BI/Warehouse_Management

Applies to:

SAP BI 7.0

Summary

If the system proposes aggregates with overlapping criteria, we reduce the overlapping proposal by optimizing them. We should check the proposals again before filling with data as the optimizer has no information on the data structure.

Author(s):  SOOREJ K V

   
Company:     YASH TECHNOLOGIES
Created on:   28 -JULY -2011
Author(s) Bio

SOOREJ KV is currently working with YASH TECHNOLOGIES (www.yash.com) as a SAP BI consultant.His expertise includes SAP BI 7.0 and ABAP.

Table of Contents

Introduction 

If the system proposes aggregates with overlapping criteria, we reduce the overlapping proposal by optimizing them. We should check the proposals again before filling with data as the optimizer has no information on the data structure.

In addition to the runtime for the queries, complete optimization must also take into account the dependencies of the aggregates, their memory requirement and the time taken to roll up new data amongst other factors.

As a part of the optimization process the numbers of aggregates are reduced. In addition, those aggregates are selected that have been called up least often and together account for 20% of all calls. These aggregates are checked, one after the other, to see if there are aggregates with exactly one extra component.

If several aggregates with exactly one extra component are found, the one with the most number of calls is selected. These are taken into account with the aggregates that have been checked. The checked aggregate is then deleted from the proposal list.

However, this only happens if the number of calls for the checked aggregate is not more than double the calls for the aggregate with the extra components. This prevents aggregates from being replaced by others that are used relatively rarely.

The optimization process is continued until the point where the aggregate is small enough, or until no more aggregates can be brought together.

Pitfalls

A proposed aggregate can contain a characteristic that is almost the same size as the InfoCube. In the above case two copies of Infocube is created which doesn’t serve any of our purpose .So it is better to check the generated proposals before filling.  

 Note: optimizer has no information on the data structure.

Related Content

http://www.sdn.sap.com/irj/sdn/nw-bi

http://help.sap.com/saphelp_nw70/helpdata/EN/10/244538780fc80de10000009b38f842/frameset.htm

http://help.sap.com/saphelp_nw70/helpdata/EN/26/4bc0417951d117e10000000a155106/frameset.htm

Useful Information

Check the overlapping proposals of aggregates before activation .