Over what period of time does SQL server activity monitor look at to recent expensive queries

Question

Suppose I run a very expensive query at 12:00pm. If at 12:01, I open SQL Server Activity Monitor and look at the recent expensive queries, I assume I'll see it there. What about 12:10? 12:30? 5pm? When will that query disappear from the view?

Likewise with execution per minute column, What period of time is averaged to find that value, and how often is it updated?

I know if you right click in the overview tab you can set your "Refresh interval" but that's not necessarily the same as the period over which data is analysed. Processes and resources waits are just a snap shot in time. But "recent expensive queries" is aggregated data from the last x minutes.

My question is how can I find what x is set to?

Answer 1

According to the documentation it is over the last 30 seconds only:

https://technet.microsoft.com/en-us/library/cc879320(v=sql.105).aspx

This pane shows information about the most expensive queries that have been run on the instance over the last 30 seconds. The information is derived from the union of sys.dm_exec_requests and sys.dm_exec_query_stats, and includes queries in process and queries that finished during the time period.