EnableRolapDistinctCountOnDataSource

We are digging into SSAS ROLAP, and based on our research, the setting that enables the database engine to manage distinct counts should be updated to 1. To adjust this feature, you have to modify the ini file and then restart the SSAS engine.

Why we made the change

Our research found two key postings, both respected SQL Server professionals:

In 2014, Karen Gulati did exploratory ROLAP work using SQL Servers new column store indexes. One key finding was to update the EnableRolapDistinctCountOnDataSource setting to 1. See: Harnessing the Power of both worlds.

Also in 2014, Hilmar Buchta did some work with SSAS ROLAP against an MSFT Parallel Data Warehouse, and determined to update the setting.
See:  Parallel Data Warehouse (PDW) and ROLAP - Hilmar Buchta.

Summary

1. Locate msmdsrv.ini
2. Make a backup of the original, unaltered ini file. (backups are our friend)
3. Locate <EnableRolapDistinctCountOnDataSource>
4. Change the setting to 1
5. Save the file and restart SSAS

Details

msmdsrv.ini

Locate msmdsrv.ini and make a backup. Typically it is located in the folder: 

C:\Program Files\Microsoft SQL Server\MSASxx.MSSQLSERVER\OLAP\Config

(where xx is the version)

Make the Change

Locate the entry for EnableRolapDistinctCountOnDataSource, make the change and save the file.

With the change made, restart the SSAS service.

Before

       
    <EnableRolapDistinctCountOnDataSource>0</EnableRolapDistinctCountOnDataSource>

After

       
   <EnableRolapDistinctCountOnDataSource>1</EnableRolapDistinctCountOnDataSource>

FIX: SSAS 2012 to back-end SQL Server 2014

We are not using this configuration, but since we did stumble upon it, we just wanted to make a note of it in case any readers are using this configuration.

FIX: ROLAP Distinct Count on data source is not started when it is running from SSAS 2012 to back-end SQL Server 2014