Hi @Anonymous ,
This needs to be discussed on a case-by-case basis, depending on how your data source is connected.
Import :You can still view the old data, a gateway failure will prevent the report from updating with new data, but will not affect your ability to view the old data.
Power BI imports the data from the original data sources into the dataset. Power BI report and dashboard queries submitted to the dataset return results from the imported tables and columns. You might consider such a dataset a point-in-time copy. Because Power BI copies the data, you must refresh the dataset to fetch changes from the underlying data sources.
Direct Query &Live Connection:When you are interacting with a report, you cannot view the report because when both modes are used, there is a real-time query to the database, which requires a gateway. For example, after the gateway fails, I go to reopen a report with a direct query connection, and when I open it, it triggers a request that is sent to the data source through the gateway, and because the gateway fails, this report cannot be viewed at this time.
Power BI does not import data over connections that operate in DirectQuery/LiveConnect mode. Instead, the dataset returns results from the underlying data source whenever a report or dashboard queries the dataset. Power BI transforms and forwards the queries to the data source.
To learn more details,refer:https://docs.microsoft.com/en-us/power-bi/connect-data/refresh-data
Wish it is helpful for you!
Best Regards
Lucien
