How do you code the TXACMRTN in the COMMAND entry point of the Top Secret Installation Exit (TSSINSTX) to issue a WTO style message?
Here it is a sample code to do that:
LA R1,CMSG
L R15,TXACMRTN
BALR R14,R15
B EXIT0
CMSG DC H'29',H'0',C'TSS0000 MESSAGE FROM EXIT'
For more information, see Extending Security Through Site Security Exits.