Hi Krishna,
This is not the direct reason for the column-store tables to be slower for data loading.
Inserting data into an 'n' column tables is like inserting data into 'n' 1 column tables and then maintaining a relationship for that record. Hence it is generally slower.
With regard to the CTL file, it will always be a row wise delimiter that will be considered because as a at the core, one needs to identify one record singularly and complex operations like aggregation comes later.
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Shreepad Patil