What do I need to define on AS400?
Assuming a normal, everyday AS/400 networking configuration, you shouldn’t have to define anything extra on AS400.
That is, of course you’ll have to have TCP/IP decently configured and running, and user IDs and authorities configured, and the host servers should be running, etc.; but those are everyday setup/configuration elements for networking.
If it’s JDBC, you shouldn’t need to do anything special.
Are you seeing problems? Is JDE signaling errors?