How Oracle Execute

If I run the procedure from the client connecting to the database server via VPN, it take 10 hours to run but if I run the same procedure at the client site it took only 1 hours, the question is VPN is problem here???? But I thought it doesn't matter where I kid off the procedure since the process resides and run right on the database server.

use sql_trace and trac it.

Is it returning data to the client?

If so you could have a network issue as its taking ages to return the data to you