Sysplex distributor addresses the requirement of providing to clients outside a parallel sysplex a single-IP-address appearance to application instances throughout the sysplex, and also the distribution of the incoming work among the various instances. Many applications are part of a cooperative network of applications, and the sysplex applications that serve as clients to users might also have to initiate (client-like) outbound connection requests to cooperating applications. The SOURCEVIPA feature allows applications to attain independence of any physical adapter, but SOURCEVIPA is limited to statically defined VIPAs within a stack. Different instances of the same application using sysplex distributor, and thus having a single IP address for inbound connection requests, will use different IP addresses for their outbound connection requests.
These problems are resolved by allowing a single sysplex-wide VIPA to be used as the source IP address for TCP applications and to have the sysplex stacks collaborate on assigning ephemeral ports to prevent duplicate connection 4-tuples (combination of source and destination IP addresses and ports). These solutions are provided by SYSPLEXPORTS, in conjunction with either job-specific source IP addressing or sysplex-wide source VIPAs for TCP connections.
For information on job-specific or destination-specific source IP addressing using the SRCIP statement, see z/OS Communications Server: IP Configuration Reference.