If you own a Distributed Relational Database Architecture™ (DRDA®) application server (AS) that will be using the TCP/IP protocol, you need to set up the DDM TCP/IP server.
Setting up the TCP/IP server can be as simple as insuring that it is started when it is needed, which can be done by running the following command if you want it to remain active at all times:
CHGDDMTCPA AUTOSTART(*YES)
But there are other parameters that you might want to adjust to tune the server for your environment. These include the initial number of prestart jobs to start, the maximum number of jobs, threshold when to start more, and so forth.
You might want to set up a common user profile for all clients to use when connecting, or set up a set of different user profiles with different levels of security for different classes of remote users. You can then use the Add Server Authentication Entry (ADDSVRAUTE) command at the application requester (AR) to map each user's profile name at the AR to what user profile they will run under at the AS.