I just upgraded our Access Manager to 4.2. Actually SP1 to SP2 to 4.2
Admin Console and Access Gateway (A+) went smooth.
The IDP died on me!
The upgrades didn't change the server.xml
catalina.out:
Jan 13, 2016 3:37:52 PM org.apache.catalina.startup.Catalina load
WARNING: Catalina.start using /opt/novell/nam/idp/conf/server.xml:
Error at (36, 67) : org.apache.catalina.core.JasperListener
Jan 13, 2016 3:37:52 PM org.apache.catalina.startup.Catalina start
SEVERE: Cannot start server. Server instance is not configured.

This is the hick-up:
<Listener className="org.apache.catalina.core.JasperListener " />

I didn't find any clues about remarking JasperListner, but doing so
revived the IDP
(Thank you, David v/d M)