IBM z/OS 2.2 PTF requirement
If you use Horizon TCP/IP for sending and receiving between Model 204 applications, you need to apply IBM PTF UI34846. Without this fix, TCP/IP client connections for Model 204 cannot be initiated.
The above PTF only affects customers that are using the Horizon-to-Horizon TCP/IP communications product. For more information about this product, see Horizon TCP/IP support.