Enclave-terminating constructs

Enclave termination can occur due to reasons other than an unhandled condition of severity 2, 3, or 4. These include:

A language STOP-like construct such as a C abort(), raise(SIGABRT), exit() function call, COBOL STOP RUN, or PL/ISTOP or EXIT statement.
When one of these statements is encountered, the T_I_S (Termination Imminent Due to STOP) condition is signaled.
A return from the main routine
A Language Environment-initiated abend
A user-requested abend (call to CEE3ABD or ILBOABN0)
You can call CEE3ABD to request an abend either with or without clean-up. If the abend is issued without clean-up, T_I_U (Termination Imminent due to an Unhandled condition) is not raised. See z/OS Language Environment Programming Reference for more information about the CEE3ABD callable service.

If you call CEE3ABD and request an abend with clean-up, or you call ILBOABN0 from a COBOL program, T_I_U is signaled. Condition handlers are given a chance to handle the abend. If the abend remains unhandled, normal Language Environment termination activities occur. For example, the C atexit list is honored if a C routine is present on the stack, and the Language Environmentassembler user exit gains control.