Dual-mode IPv4/IPv6 stack

When both AF_INET and AF_INET6 are coded in BPXPRMxx and a dual-mode-capable stack is started, both AF_INET and AF_INET6 sockets are supported by the stack, and applications can send and receive IPv4 and IPv6 packets.

Requirements: To enable AF_INET6 support in an integrated sockets environment, the following two conditions must exist:

AF_INET6 must be configured in BPXPRMxx. Note that AF_INET6 support can be dynamically enabled by configuring AF_INET6 in BPXPRMxx and then issuing the SETOMVS RESET= command to activate the new configuration.
A dual-mode capable stack must be started after AF_INET6 is configured in BPXPRMxx. If a TCP/IP stack that is capable of being a dual-mode stack is started before BPXPRMxx is configured, the stack remains an IPv4-only stack as long as it remains active; however, if the stack is stopped and then restarted, it restarts as a dual-mode TCP/IP stack if AF_INET6 is configured in BPXPRMxx at the time it is restarted.

Requirement: To enable AF_INET6 support for z/OS® Communications Server TCP/IP, z/OS Communications Server TCP/IP must be started as a dual-mode stack. z/OS Communications Server TCP/IP does not support being started as an IPv6-only stack. In other words, if AF_INET6 is coded in BPXPRMxx, AF_INET must also be coded. If it is not, then the z/OS Communications Server TCP/IP stack fails to initialize.