Update Kernel on dual stack ABAP + JAVA

Hi

we have NW2004s dual stack ABAP and JAVA and we want to upgrade the kernel. ABAP is non unicode

1. Since ABAP is unicode I guess we have to apply a unicode kernel. But where we are confused is that JAVA is always unicode

2. In the system there are several directories containing kernel binaries

/sapmnt/P81/exe

/sapmnt/P81/exe/nuc/hpia64

/sapmnt/P81/exe/uc/hpia64

/usr/sap/P81/DVEBMGS00/exe

/usr/sap/P81/SCS01/exe

Why do we have a uc and nuc directories since our ABAP is non unicode ?

We are familiar with ABAP kernel but what is a JAVA kernel what binaries it contains ?

3. Is kernel update can update also the config tool or visual admin ? or theses components are never updated ?

4. If we decide to update the kernel manuall can we just extarct the non unicode kernel to /sapmnt/P81/exe ?

5. If we use JSPM to update the kernel does it stops ABAP instances or only JAVA instances ?

Thak you for your help.