Hi Gurus,
I am working on cognos migration project.I need to migrate my impromptu Catalog to Cognos FM model and create the reports.
I had one Catalog and it contains 80 tables and all joins are in outer join method,now i need to migate the same to Cognos 8 model and i did the same,I know that having outer join makes all the problems in reports i performance,can any one just suggest me to make my model optimized.
What all the points i need to note from Cognos 7 catalog and how can i make it optimized pls help me out.
Thanks in advance,
K.M
Just some thoughts:
Quite often joins are set as outer join, cause no time has been spent on the analyzing the data underneath. If a FK is designed to be nullable , then an outer join will be in order to avoid 'losing' rows in the join process. If the FK is not nullable, then an outer join is often unneeded, especially if you only are interested in only making sure to fetch values from dimension tables for all fact rows.
So, if the model uses outer joins only, you may be able to optimize by setting cardinality properly where an inner join suffices.
Simply rebuilding the C8 model by mimicing the Catalogue may introduce differences in SQL generates, as the C8 model will try to work in cardinality settings (even if you do not define determinants).
The best approach is to remodel by working towards starschema's. This may involve combining tables into new model query subjects..
Thanks a lot for your kind information.I follow the steps you suggested to create the optimized model.
Thanks
K.M