Figure 1 illustrates how z/OS UNIX determines if a signal is enabled, ignored, or blocked. A few POSIX signals do not go through this process. See POSIX signals that do not enter condition handling for details.

If a signal is ignored or blocked, the signal does not enter Language Environment synchronous condition handling. If a signal is enabled, z/OS UNIX passes it to the Language Environment enablement step (described in Enablement step). From there, Language Environment either disables the signal, or passes it into the Language Environment condition step.

Figure 1. Enablement step for signals under z/OS UNIX