Hi Kaniz 
I have one more issue , i am writing less than 1.2k records to the datalake table (append mode). While writing it is showing "determining dbio file fragments this would take some time', when i checked the log i see GC allocation failure  .
and my overall execution time is 20 mins which is hard for me , how can i resolve this , ? is it mandatory to use Vaccum, Analyze queries along with Optimize
shall i run optimize datalake.table ?