> I have a table with over 6 milions rows. In one the function in my application, I will purge all rows and re-insert new rows to the tables. After I run "DELETE FROM table", all further operations will become very slow as the database is sweeping the database.

If you need to purge these rows, there is no pint to insert them at
all. May be you should look at Temporary Tables?..

SY, SD.