Hi @Hanae TAHRI ,
Thanks for your posting!
Your question is related to Power BI, so I suggest that please post your question in Microsoft Power BI Community that can help you get answers more quickly. Thank you.
In addition, from SSAS aspect, it is possible to improve Power BI performance via SSAS. For more information, please refer to below link:
Microsoft Power BI: Tabular Model Optimization
If a model is becoming too large and the query duration rises as the model size grows it can become interesting to add an aggregation table. Such a table will be aggregated before being loaded into a tabular database and will give a more high-level view of the data. This way reporting will be faster because a lot of the calculations are done beforehand. As a downside model processing will take longer.
This can also be done for calculated tables and columns. These increase model size and result in longer refresh times. If possible, it is always best to limit the use of calculated objects and create/calculate them in the data source. Even if the calculation of this table or column happens in a view, it only needs to be calculated when the model is processed.
Keep your model slim
Remove unnecessary tables and columns. They take up resources and raise processing time. It is better to add them later. Adding something is fairly easy.
Avoid using only one model when multiple models make more sense. This will allow you to optimize each model for its specific purpose. Optimizing one model for recent detailed data and another model for a global high-level overview will result in a much better performance than trying to fit it all into one model.
Properly set meta-data properties
Change the “Summarize By” property for all fields that do not need to be summarized. A field like Year will automatically be recognized as a numeric field and Power BI will summarize this field. Which is annoying for users and has a serious negative impact on performance if data is shown on a low level of granularity. For big models it is advised to avoid implicit “Summarize By” measures and always create an explicitly defined measure.
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