I know this is a old question already answered to an extent, but am adding a further answer to the open question left by the OP.

I am not sure of the system environment. But DB2 needs user usable "USER TEMPORARY TABLESPACE" defined before TEMPORARY tables can be created. "LIST TABLESPACES" should give you the list of tablespaces which are available and atleast one of them should be "system managed space" for User temporarty data". If such tablespace doesnt exist, one can be created by an Admin and the issue of being unable to create a GLOBAL TEMPORARY TABLE should be solved.