Poor Processing Performance after Migration from SSRS 2005 to SSRS 2014

Question

Hello all,
a customer is moving from SQL Server 2005 to SQL Server 2014 (clean install on a new machine). There are a lot of reports against an Analysis Services database. I have converted and deployed the reports. Most of them are showing a significant performance
improvement, but some of them became very slow.
Analyzing the report server's execution log I have discovered that the rendering time has increased very much (see picture for a specific report below - above the blue line is SSRS 2005 on an older machine, below is SSRS 2014 on a new machine).
Do you have any hints what I can do?
Thanks in advance and best regards,
Gerald

Answer 1

Thank you for your reply. Cumulative Update 4 has already been installed (I have just compared the installed version number with the list on
sqlserverbuilds.blogspot.com).
My first suspicion was also a rdl conversion problem. But as even reports with a blank page where showing this rendering performance problem I began to look at the datasets (although they are executed very fast according to the report server's
execution log view).
All MDX queries have been designed using the
Analysis Services MDX Query Designer. The option for not showing empty cells is activated to supress empty rows. But this option always applies to both axes (when usings the query designer). Thus columns for measures with null values in all rows are omitted
from the result set. When rendering a report the rsMissingFieldInDataSet-Error is shown, but in SSRS 2005 and also in the Data Tools for SQL Server 2014 this has no further impact.
But SSRS 2014 is performing very bad in this case. If I remove the NON EMPTY clause for the columns (which only works when switching to the text query builder, so the customer is not able to modify the queries anymore) the report performance will be as expected.
So far there're only two reports left where this does not solve the performance issue.
During testing I have also observered the BIDS - SQL 2008 R2 Warnings not clearing-bug which can be reproduced by everyone except
Microsoft ;)
Regards,
Gerald