Parallelization in TDV fails with Reason: Plan has scans with low estimated data volumes. We can see this message on the top-level SELECT node in the Query Execution plan.
This indicates that the query seems to be fetching low volumes of data from the underlying data source. 

 

To resolve this, follow the steps:

1. Browse to Studio > Administration > Configuration > Server > Configuration > Debugging > Parallel Processing > Disable Low Data Volume Restriction
2. Change the value to “True”
3. Click “Apply” and close the window

Screenshot for reference:

Change the configuration setting as mentioned above, and then test the query.

Note: 
Queries handling data of low volume are typically not handled by the parallel processing engine. This is because if the datasets are small, then using the MPP Engine will result in an overhead of setup time, unnecessary routing of data to different nodes and also to combine them back at runtime. In such a situation, using the classic engine gives the best results.