https://forums.oracle.com/forums/thread.jspa?threadID=2177895&tstart=90
As far as i have worked on EF4 using Oracle , Function importing doesn't seems
to work here. I faced the same problem few months back and tried many ways to
import a function but without any luck. But during searching I found a link on
OTN which states that (Oracle Stored Functions are not
supported). EF4 doesn't give us the option to call oracle function yet.
Even using Stored Procedures, you will need to select stored procedures that
return a ref cursor. Supported Stored procedures include procedures and package
methods that do not have a return value, but may have OUT or IN OUT parameters.
http://www.oracle.com/technetwork/issue-archive/2011/11-sep/o51odt-453447.html