The InterFormNG servers are running in the IFORMNG subsystem. You simply stop or start the servers by stopping or starting the subsystem from the menu or via these commands:

ENDSBS IFORMNG

STRSBS IFORMNG/IFORMNG

It is advisable to setup start of the IFORMNG subsystem in the IPL program in QSTRUPPGM - remember to add a MONMSG CPF0000 to ensure that the IPL program can run even this subsystem cannot be started.