This command is used any time you want to stop a query that is in process. You may want to cancel a query that is taking a long time to complete due to the size of the data source. When a query is taking a long time to complete, a progress dialog box opens. You can cancel a requested query by clicking the Cancel button on the Processing Request dialog box.
To cancel a query:
Click Cancel in the Processing Request dialog box.
After canceling a query the view becomes invalid because it is in an in-between state. The result is a blank view although all your fields are still on the shelves. To resume working with Tableau, alter the view in anyway and allow the query to complete.
Canceling a large number of queries can result in performance degradation in the underlying database. Although the query has been abandoned by Tableau, it is still executing on the database.