User-named triggers are invoked by calling the EXECUTE_TRIGGER Built-in subprogram:
/* Built-in Trigger: */
statement a;
Execute_Trigger('my_user_named_trigger');
statement b;
When an unhandled exception is raised in a user-named trigger, the user-named trigger fails, but the exception does not propagate to the calling trigger. Rather, Oracle Forms treats the failure as an error in the Built-in procedure EXECUTE_TRIGGER, and sets the return values of the Built-in error functions accordingly. Thus, the outcome of a user-named trigger can be trapped in the same way as a call to any other Built-in subprogram; that is, by evaluating the Built-in error functions:
/* Built-in Trigger: */
statement a;
Execute_Trigger('my_usernamed_trigger');
IF NOT Form_Success THEN
RAISE Form_Trigger_Failure;
END IF;
statement b;
About using PL/SQL exception handling in triggers
About evaluating the success or failure of Built-ins
Handling errors in Built-in subprograms