Many POSIX tasks can be created using the fork mechanism of the POSIX subsystem. Such POSIX tasks can be controlled independently of the other batch and dialog jobs.
The JMU statement SET-POSIX-JOB-CLASS-DEFAULT (see "Utility Routines" [17] manual) enables individual or all user IDs to be assigned a default job class for POSIX tasks. This job class must have been defined beforehand using DEFINE-JOB-CLASS. If no POSIX default job class is defined, the behavior in the case of fork remains unchanged.
Example:
/START-JMU //SET-MODIFICATION-MODE ... //SET-POSIX-JOB-CLASS-DEFAULT - // NAME=JCBPSX1, ACTION=*ADD, USER=*ALL ———————————————————————————— (1) //SET-POSIX-JOB-CLASS-DEFAULT - // NAME=JCBPSX0, ACTION=*ADD, USER=(TSOS,SYSROOT) —————————————————— (2) //END
(1) | A POSIX default job class which is valid system-wide for all user IDs is defined. |
(2) | A different POSIX default job class is defined for the user IDs TSOS and SYSROOT. |
With the conventional way of defining default job classes for BATCH or DIALOG using the JMU statement SET-JOB-CLASS-DEFAULT, a job class becomes the default job class either for batch or dialog tasks according to its definition (JOB-TYPE=). This distinction is not made for POSIX default job classes; the type of job class is arbitrary. A POSIX task generated by fork is assigned the task type of the parent task and the category of the job class in which it runs, i.e. the POSIX default job class.
If the parent task is not running in a default job class (POSIX, DIALOG or BATCH) when the fork takes place and the child task has the same user ID as the parent task, the child task is not assigned the POSIX default job class, but the job class of the parent task.
The POSIX default job classes apply only for the POSIX tasks generated by fork. POSIX programs which are started in batch or dialog tasks, e.g. with START-PROGRAM, run in the job class of this batch or dialog task. This applies in particular for POSIX access using the START-POSIX-SHELL command.