Dear Rajat ,
QCM Tables should be deleted before starting the migration ,
check the following SAP note
9385 - What to do with QCM tables (conversion tables)
to delete QCM tables. call transaction SE14 and select 'Extras->Invalid temp. table' in the menu bar This displays all the QCM tables that can be deleted. You can highlight these and choose a pushbutton to delete them
Best regards
AhMeD