All you need to make sure is that the SAP APPLICATION SERVER JAVA takes the new JDK (the jvm switch tool shuld take care of this).
Else:
Edit the instance profile and change the profile parameter
SAPJVM_VERSION. Enter the new version of the SAP JVM e.g.:
SAPJVM_VERSION = 4.1.028
and
jstartup/vm/home = <location of the new jdk>
for example:
jstartup/vm/home = /usr/sap/<SID>/SYS/exe/jvm/hpia64/
sapjvm_4.1.028
Regards,
Hemanth