SQL & PL/SQL

Hi Folks,
As per my understanding there is no performance wise difference between the normal cursor and ref cursor the only difference is that only through the help of the refcur we can return the result set to the calling env or calling procedure.
But in OTN site one of the excerpts from Tom I came across a statement that the refcursors can not be global means we can not declare the refcur in the package specification
the link is http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:14188501024541
but many times in my project we have declaree the refcursor in the package specifications also
Can any one explain me what Tom really meant by that statement or whether I am misinterpreting the statement


Any suggestions will be highly appreciated

Thanks in advance

Prafulla