Assuming that every necessary configurations are done at the zO/S, i.e. communication connectivity, authorizations, etc. It is blindly simple to set up DB2 LUW to talk to DB2 OS/390.
You just need to do the following in DB2 Command Window (Let say in Windows).
db2 catalog tcpip node NODE1 REMOTE
SERVER OSTYPE OS390
db2 catalog dcs database
db2 catalog database
Ok, and if previously the utility packages are not bind yet, you might hit errors when try to run even simple commands in DB2 OS/390. To fix this, You will need to change directory to your
db2 bind @db2ubind.lst blocking all grant public
db2 bind @db2cli.lst blocking all grant public
db2 bind @ddcsmvs.lst blocking all grant public
Again, I will ask "Simple right?" ;-)