Setting communication protocols for a DB2® instance is part of the main task of configuring TCP/IP or SSL communications for a DB2 instance.
The DB2COMM registry variable allows you to set communication protocols for the current DB2 instance. If the DB2COMM registry variable is undefined or set to null, no protocol connection managers are started when the database manager is started.
To set the communication protocol for the instance:
db2set DB2COMM=tcpip
db2set DB2COMM=tcpip
db2stop
db2start