I had this requirement where I had to pass the url generated in OAF to Java script. In Javascript I have a link, when clicked needs to go back to OAF page. The problem I had was when I pass just "OA.jsp?OAFunc=<functionname> it was throwing me an error.

You are trying to access a page that is no longer active.
- The referring page may have come from a previous session. Please select Home to proceed.

Then I found out that a new parameter oas needs to be also passed.

Import the below statements:

import oracle.apps.fnd.framework.server.OADBTransactionImpl;
import oracle.apps.fnd.common.URLTools;
import oracle.apps.fnd.common.WebAppsContext;

Below code will help to generate the url with oas parameter:

String sourceUrl="OA.jsp?OAFunc=<function name>
      WebAppsContext wctx = (WebAppsContext)((OADBTransactionImpl) pageContext.getApplicationModule(webBean).getOADBTransaction()).getAppsContext();
      String secureUrl = URLTools.generateSecureURL (sourceUrl, wctx);