SFTP requires SSH plus the implementation of a protocol. As far as my PL/SQL knowledge reaches and Google's, there are currently no available implementation of SSH or this protocol in PL/SQL. There are some alternatives:
- Use Java in the database and open sufficient ports. Not recommended when this is the only reason to use Java in the database; it is not as well designed as PL/SQL and can be expensive to maintain by a DBA since most DBA's have no experience with it.
- Use PL/SQL to start a job outside the database. For instance, in the past I've used often Pentaho Data Integration (formerly known as Kettle) which provides a free solution to draw your data flow from table/procedure to sftp recipient and then run it. Running from PL/SQL requires a scheduler (I always used our own because it also integrates Kettle, but you can also consider the scheduler integrated with Oracle Apps, Redwood JCS/Cronacle or others). Coding in PL/SQL then becomes something like: 'begin package.submit('SFTP it'); package.wait; end;'.
I would go for the second option. If you need further details, please let me know.