I am redesigning the physical storage of a big table. I am evaluating MDC and/or partitioning cenarios. When I have a column which would be very suitable it is only usefull when that same column is used in the "WHERE clause" often. I do not know the application very well but that infomation is present in the package cache..... but how do I get it out. Any suggestions?

get snapshot for dynamic sql or db2pd -d <dbname> -dynamic

you can also use event monitor to capture statemts.
if you are using stored procedures with static sql, you may have to use syscat.statements too

Design Advisor might help to decide for/against paritioning ..