I'm not 100% sure of what your asking. However you can change the CODEPAGE in the DB2 registry by using db2set. The parameter you are interested in is
DB2CODEPAGE - As I understand it, this is on all Windows/UNIx platforms. If it is not set, DB2 will use the code page set for the operating system.
You may find the following useful
db2set - lr
to view a list of all variables that can be set in the profile registry.
Cheers
Greg