There are times when you need/must inform all logged on users of some system update. This is typically used to inform users of a planned system outage so that they can to a planned logoff.
From the operator console the SEND command will do that.
Example: send 'text' now will send the text to all loggedf on TSO users.
It will not send messages to logged on ssh users - to do that you need to use the wall shell command. This can be accomplished by logging in using ssh or using a System REXX script that uses bpxwunix.
Example: wall text
The wall doc indidates you need to be superuser1 to send (write) to all the ttys - otherwise you're only sending the message to yourself which is kinda like talking to yourself.
Here is a sample REXX code that could be used for a TSO User, or using a System REXX console command, to send a message to all ssh and all TSO users:
/* rexx */
parse arg message
"CONSPROF SOLDISP(no) SOLNUM(400) UNSOLDISP(yes)"
"CONSOLE ACTIVATE"
"CONSOLE SYSCMD(SEND '"message"' NOW) "
"CONSOLE DEACTIVATE"
address syscall 'geteuid'
myeuid=retval
Address syscall "seteuid 0"
cmd = "wall '"message"'"
x = bpxwunix(cmd,,s.,e.)
Address syscall "seteuid" myeuid
#IBMChampion