In a single stack environment, the socket application program is always associated with the single TCP/IP stack. Figure 1 shows an example of a z/OS UNIX system that uses a single stack.

Figure 1. A z/OS UNIX system using a single stack

The TYPE(INET) parameter on the FILESYSTYPE statement defines INET.

INET is defined by the presence of a FILESYSTYPE statement for a socket file system whose ENTRYPOINT is not BPXTCINT. By convention, and in this topic, TYPE(INET) parameter for INET configurations is specified. The entry point for INET is typically EZBPFINI, for z/OS® Communications Server (TCP/IP Services).