1. create another TCPIP.DATA dataset from the current production TCPIP.DATA say, the new one would be SYS1.TCPPARMS(TCPDATA)

We expect SYS1.TCPPARMS(TCPDATA) to be the new production TCPIP.DATA and you have the HOSTNAME updated in there.

2. find sample HLQ.SEZAINST(EZBRECNF) and copy this member to whatever you called, say, SYS1.PARMLIB(SETUP) there are two importment statement in this member we can point to the new TCPIP.DATA dataset, which is GLOBALTCPIPDATA and DEFAULTTCPIPDATA, for example, for your requirement, you might just need one statement such as

GLOBALTCPIPDATA(SYS1.TCPPARMS(TCPDATA))

3. in the operator console, issue command

F RESOLVER,REFRESH,SETUP=SYS1.PARMLIB(SETUP)

cosole should respond with message like below

EZZ9298I GLOBALTCPIPDATA - SYS1.TCPPARMS(TCPDATA)

EZZ9298I DEFAULTIPNODES - None

EZZ9298I GLOBALIPNODES - None

4. if you later on change mind and want to return back to the original TCPIP.DATA go back to SYS1.PARMLIB(SETUP) and comment out every statement then do a refresh command again,

F RESOLVER,REFRESH,SETUP=SYS1.PARMLIB(SETUP)

console will respond with message like below

EZZ9298I DEFAULTTCPIPDATA - None

EZZ9298I GLOBALTCPIPDATA - None

EZZ9298I DEFAULTIPNODES - None

EZZ9298I GLOBALIPNODES - None

which tell us we are not using GLOBALTCPIPDATA at all, everthing back to what used to be, regular MVS & UNIX resolver search order as it was.