Changing sql-server DB from tabular to multidimensional
Tabular and Multi Dimensional are completely different thing. When you install SQL Server, you have to choose which one you are going to install.
So, if you create a Tabular model, you only can deploy it to Tabular installation of SSAS and the same for Multi Dimensional
you can not convert those model to each other.
All you have to do it go edit the MSMDSRV.ini and change the deployment mode to either (0,1,2,3) depending on what you are trying to use. Also remember that you have to log off the SQL studio and log back in.
It is possible to stop SSAS, edit the msmdsrv.ini and change DeploymentMode from 2 to 0. Empty the DataDir folder. Then start SSAS. This will change the instance from Tabular mode to Multidimensional mode. It will not convert models.
Cathy Dumas describes the reverse here.
Best recommendation is to reinstall only SQL Server Analysis Services feature without disrupting other features/components like SQL Server Engine. During reinstallation of the feature we can change the configuration of Analysis Services to Multidimensional and Data Mining Mode. The whole reinstall process takes less than 10 minutes. So, this approach is easy and quick.
I'm enlisting all the steps for SQL Server 2017 installation:
Go to Add Remove Program (ARP) Window in control panel. Select the row for Microsoft SQL Server 2017 (64-bit) and click on Uninstall/Change
It'll open the SQL Server 2017 change wizard as shown in the screenshot below:
Click on Remove link
Select Analysis Services for removal:
Complete remove action by following the wizard.
Restart from step 1 but this time click on Add link to start installation wizard.
During feature addition it'll ask for the location of SQL Server setup files (which can be in your hard disk, CD, or a mounted virtual drive)
Reinstall SQL Server Analysis Services feature. On the Analysis Services Configuration step, go to Server Configuration tab and select Multi-dimensional and Data Mining Mode as shown in the screenshot below:
Click Next > and complete the wizard.