Hi @Divya904,
Let's make it simple.
1. No data is stored in the Desktop;
2. Only queries are sent to the data source when necessary. For example, render a visual, refresh report.
3. Addition to 2, only queries are sent to fetch data. That means most part of the work will be done in the data source.
Please refer to #directquery-connections for details.
>>>However, upon load, no data will actually be imported into the Power BI store. Instead, upon building a visual within Power BI Desktop, queries will be sent to the underlying data source to retrieve the necessary data. The time then taken to refresh the visual will depend on the performance of the underlying data source.
About the data type conversion, please refer to #limited-data-transformations.
>>>First, when connecting to an OLAP source like SAP Business Warehouse, no transformations can be defined at all, and the entire external ‘model’ is taken from the source.
>>>For relational sources, like SQL Server, it is still possible to define a set of transformations per query, but those transformations are limited for performance reasons.
>>>Any such transformation will need to be applied on every query to the underlying source, rather than once on data refresh, so they are limited to those transformations that can reasonably be translated into a single native query. If you use a transformation that is too complex, then you will receive an error that either it must be deleted, or the model switched to Import mode.
Best Regards,
Dale
Community Support Team _ Dale
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