BI Upgradation

Dear All,

We are going to upgrade from 3.0b to BI 7.0 for FICO and PM.

Can anybody share your experience abt the same upgradation. So that we can be aware of the problem. I am just go throughing some OSS notes.

What is the JAVA stack and ABAP stack. In 3.0B we have ABAP program only. what is the use of JAVA. Is it mandatory to have JAVA in BI??

Help me to know more abt the precaution to take before upgradation.

Thanks in advance.

Esther