Environment used: two Oracle 12c databases (productive and development/testing). To replicate data of some particular tables on demand from prod to dev, we plan to use a database link. Some tables are relatively big ~1G, so its is not clear on which database the link should be created to have a minimal impact to transactions/performance on production? Or does it make any difference at all?
If you want to move data around, consider using a tool which is designed for that - Data Pump. Export data from the production database and import it into development. It works at the operating system level, but user - that performs that operation - should have access to directory (Oracle object which points to a filesystem directory, place where export file (DMP) and log file are located).
Database link presumes that you know login credentials of the "target" database. So, if you create a database link from development to production, you'd pull data to development database. However, there's a risk that developers will be able to destroy production data (delete tables, truncate them, update values, ... anything they want). So, that's not exactly "performance" problem but security issue.
Vice versa? Production should push data to development.
Once again: I'd use Data Pump.