Usage in a parallel sysplex

z/Server itself does not use any sysplex services. It relies on the ability to connect to an IP address specified using a TCPIP header. This is normally done under the covers by an Eclipse client:

  1. The Eclipse client asks for "Connect" to an IP address (or symbolic name) using a port specified in the client. This port corresponds to the PORT parameter that the scheduler address space listens on. As a response, z/Server sends back the IP address of the system that this particular scheduler address space runs on.
  2. The next transaction initiated from the client (which includes the TCPIP function connect - different from the function "Connect" in 1.) uses this IP address for further communication and (IP-)connection.
  3. As long as the network is set up in such a way that usage of this IP address will guarantee connection to the same host system, the first connection used (from the Eclipse function "Connect") z/Server functions without problems.

Note that it is mandatory to have a one-to-one relation between the IP address and the system name. A configuration where an IP address can resolve to different systems (for load balancing, for instance) is not supported. (See also VIPA).