DTP-extraction-tab:Check-box 'use aggregates' what does it mean?

Question

Hello BW experts
Can someone explain in simple words, what das it mean the check box  'use aggregates'  in the data transfer process (Tab extraction).
The F1-help gives the following explanation  -however I don't understand the info-:
'Should aggregates be used? This also means that an additional selection condition is automatically inserted that restricts to rolled up data requests.'
Best regards and thank you to help to understand
Christian
PS: We are loading data from cube to cube
Edited by: Christian Baumann on Jan 9, 2009 9:24 AM
Edited by: Christian Baumann on Jan 9, 2009 9:26 AM
Edited by: Christian Baumann on Jan 9, 2009 9:27 AM

Answer 1

Hi Christian,
I have never tried it myself , but I guess, it would mean if aggregates are built on the cube from which the DTP was extracting data you could choose to extract data from the aggregates instead.
The aggregates are the same as a cube, but with fewer characteristics and would hold data at a summarized level.
If this summarized level is sufficient for load to downstream infoproviders you could choose to extract from the aggregates.
This would mean lesser data is read during extraction and extraction would be faster.
SAP excerpt
With InfoCubes as the source: Use extraction from aggregates
With InfoCube extraction, the data is read in the standard setting from the fact table (F table) and the table of compressed data (E table). To improve performance here, you can use aggregates for the extraction.
Select data transfer process Use Aggregates on the Extraction tab in the DTP maintenance transaction. The system then compares the outgoing quantity from the transformation with the aggregates. If all InfoObjects from the outgoing quantity are used in aggregates, the data is read from the aggregates during extraction instead of from the InfoCube tables.
Regards,
Sunmit.