Table to Table load is slow!

I have 2 similar column tables (say Tab_A & Tab_B). At any given point of time, one of them will be used by the users and the other gets modified with new data.

Trouble I have here is, both the tables contain approx. 50M records. When I try to load the 50M records into a table (33 columns in each), HANA is taking around 20 minutes!

All that I'm doing is:

Delete from Tab_A;

Insert into Tab_A Select * from Tab_B;

Where Tab_B contains 50 Million records.

Any suggestions for improvements in the code ??

Thanks,

Varun