I need to query 3.5 million rows from remote database on a regular basis. Query will take subset of columns with or without condition.
I am still not sure the way Oracle will behave when data are queried across db link: will all rows with all columns be moved, or will it be transfer all rows with requested subset of columns, or ...?
I did notice speed up if querying a view on remote database comparing with executing full statement locally.
Any advice on what could be the most efficient way of transferring large amount of data via db link.
Or maybe instead of using db link, I do spool and load data !?