How to see, if a foreign key is enforced?
Not sure what version of db2 you are using, but if it's LUW you can use SYSCAT.TABCONST (see column ENFORCED):

select enforced 
from syscat.tabconst 
where tabschema = ?
  and tabname = ?
  and constname = ?


FWIW, it is better to use the syscat views (vs sysibm), since they are more stable between versions.