Sometimes for a variety of reasons, a refresh database query on the server may be running for too long and there is no easy way to gracefully kill the process. If Tableau server is to truly serve as an enterprise data provider then there should be a better way to handle the management of the background tasks.
Note - the following are duplicate ideas and their vote scores should be included in the score noted here:
151 Votes http://community.tableau.com/ideas/2657
Total of 297 Votes