Re: How does the system use multiple cores or processors?

Hello Darryl,

Am 05.06.2023 um 21:22 schrieb a4g atl <a4ginatl2@xxxxxxxxx>:

I have had conflicting opinions.

Do we have to code specifically for multiple cores or does the OS handle using multiple cores transparently?

The question is for a single LPAR.

As always, "it depends".

If your LPAR has more than one logical CPU assigned, they will be utilized as long as there are separate jobs/applications/processes asking for CPU time. Example: You can submit two batch jobs, the system runs each one on a separate core, in parallel. (Note: You need to configure your job queue accordingly to allow more than one job being run in parallel.)

If you have a single application program (in RPG, for example) which is doing something, this will never automatically parallelize. That's when you need to either use the easy way, and split that one task into subtasks in separate application programs, allowing the OS to parallelize. Or you need to introduce threads in your application, allowing for parallel execution within your single application.

From earlier discussions on this list, I remember using threads in RPG is not that easy to implement and thus rarely exploited. Also, there's a certain limit on "things" you can run parallel, in the scope of a job consisting of multiple applications. Most often you need the result of a previous job step for the next one, in turn nullifying the capability to parallelize.

This is a somewhat simplified explanation but it should provide an adequate answer.

:wq! PoC