SSRS Report queries begin running slowly, have to stop and start report server to restore performance

Question

We have had a production issue crop up twice now where reports begin running slowly seemingly at random.  
When this happens we can see from running SQL Profiler that the report queries are taking an extremely long time to execute.  The same queries when run directly in management studio run quickly.  
Initially I suspected parameter sniffing, and tried using OPTION (RECOMPILE) in the reports, as well as clearing out the particular query from the plan cache and running the SQL in SSMS to try and get a better plan etc but no amount of jiggery pokery by
me could get the queries to run any faster.
The really weird thing - is that stopping and starting the report server via the reporting services configuration manager instantly cures the problem.  
I'd really love to know - why this might be?  Is it something to do with the report server closing and re-opening its connections to the database? That's the only sort of thing I can think of...any ideas? Anyone? Any suggestions would be much appreciated.
LucasF

Answer 1

Hi LucasF,
In your scenario, usually we can monitor the execution log in Report Database. If you run below query, you can get the results how long the report takes to render (TimeRendering), how long to process the report(TimeProcessing) and how long to retrieve data
from Database(TimeData). You can check the starttime and endtime to know the total time for executing a report.
SELECT TOP1000 *FROM[ReportServer].[dbo].[ExecutionLog2]
More details information, please reference to similar thread below:
Steps for troubleshooting a slow SSRS 2014 server
Troubleshooting Reports: Report Performance
In SQL Server Reporting Services, a job will be created by SQL Server Agent if any of the following processes is underway:
query execution on a remote or local database server
report processing
report rendering
To cancel a job that is running on the report server, we can cancel the job directly or reduce the report execution time-out value in the SQL Server Management Studio and then will stop query execution. Please refer to the steps below:
Open SQL Server Management Studio, and connect to "Reporting Services".
Under the Report Server node, right-click on the "Jobs" folder and select "Refresh". Then, right-click on "Jobs" again and click "Cancel All Jobs".
Right-click on the Report Server node and open the "Server Properties" dialog.
Click the "Execution" option, and set the "Limit report execution to the following number of seconds:" to a much smaller number. After this issue is resolved, this configuration should revert to the previous state.  
Reference:
Managing a Running Process
Setting Time-out Values for Report and Shared Dataset Processing
In addition, we can also use the KILL Transact-SQL statement to terminate a normal connection by terminating the transactions that are associated with the specified session ID. For the details information, you can refer to:
KILL (Transact-SQL)
If you still have any problem, please feel free to ask.
Regards,
Vicky Liu
Vicky Liu
TechNet Community Support